Nonvolatile magnetic memory device and photomask

ABSTRACT

Disclosed is a nonvolatile magnetic memory device including a magntoresistance device having a recording layer formed of a ferromagnetic material for storing information by use of variation in resistance depending on the magnetization inversion state. The plan-view shape of the recording layer includes a pseudo-rhombic shape having four sides, at least two of the four sides each include a smooth curve having a central portion curved toward the center of the pseudo-rhombic shape. The easy axis of magnetization of the recording layer is substantially parallel to the longer axis of the pseudo-rhombic shape. The hard axis of magnetization of the recording layer is substantially parallel to the shorter axis of the pseudo-rhombic shape. The sides constituting the plan-view shape of the recording layer are smoothly connected to each other.

BACKGROUND OF THE INVENTION

The present invention relates to a nonvolatile magnetic memory device,and a photomask for use in the manufacture of the nonvolatile magneticmemory device.

Attendant on the drastic spread of personal small apparatuses such ascommunication apparatuses, particularly, the personal digitalassistants, various semiconductor devices such as memories and logicalcircuits constituting the apparatuses are desired to have higherperformance, such as higher degree of integration, higher operatingspeed, lower power consumption, etc. Particularly, nonvolatile memoriesare considered to be keenly desired in the ubiquitous computing age.Even in the cases of consumption or trouble in the power supply or inthe cases of cutoff between a server and a network due to some disorder,the nonvolatile memory makes it possible to preserve and protectimportant information. In addition, while the recent portableapparatuses are designed to suppress power consumption as much aspossible by putting unnecessary circuit blocks into the stand-by state,if a nonvolatile memory capable of functioning as both a high-speed workmemory and a large-capacity storage memory can be realized, it ispossible to eliminate the wastefulness in power consumption and memory.Besides, the “instant-ON” function enabling an instantaneous start uponmaking the power supply can also become possible if a high-speedlarge-capacity nonvolatile memory can be realized.

Examples of the nonvolatile memory include flash memories usingsemiconductor materials, and ferroelectric nonvolatile semiconductormemories (FERAMs, Ferroelectric Random Access Memories) usingferroelectric materials. However, the flash memories have the defectsthat the write speed is on the order of microseconds, which is lowerthan desired. On the other hand, the FERAM has a number of times ofoverwriting possible on the order of 10¹² to 10¹⁴, which is too low forthe FERAM to be used in place of SRAM or DRAM, and there is the problemthat micro-processing of the ferroelectric material layer is difficultto carry out.

As a nonvolatile memory free of the above-mentioned defects, thenonvolatile magnetic memory devices called MRAM (Magnetic Random AccessMemory) has come to be paid attention to. The MRAM in the early stagehas been based on a spin valve using the GMR (Giant Magnetoresistance)effect. However, the early MRAM has the drawback that, since the memorycell resistance of the load is as low as 10 to 100 Ω, the powerconsumption per bit at the time of reading is large, and it is difficultto increase the capacity.

On the other hand, the MRAM using the TMR (Tunnel Magnetoresistance)effect has come to be paid attention to in recent years, since theresistance variation ratio at room temperature has been improved toabout 20%, from the values of about 1 to 2% in the beginning stage ofdevelopment. The TMR type MRAM is simple in structure, promises easyscaling, and has a large number of times of overwriting possible becauseof the recording by rotation of the magnetic moment. Furthermore, withthe TMR type MRAM, a very short access time is expected, and it is saidthat the TMR type MRAM has already come to be able to operate at a rateof 100 MHz.

A schematic, partly sectional view of the TMR type MRAM (hereinafterreferred to simply as MRAM) is shown in FIG. 6. The MRAM includes atunnel magnetoresistance device TMJ connected to a selection transistorTR including a MOSFET.

The tunnel magnetoresistance device TMJ has a laminate structure of afirst ferromagnetic material layer 31, a tunnel insulation film 34, anda second ferromagnetic material layer 35. More specifically, the firstferromagnetic material layer 31 has a two-layer structure of, forexample, an antiferromagnetic material layer 32 and a ferromagneticmaterial layer (also called the anchor layer or magnetization fixationlayer) 33, in this order from the lower side, and has a strongunidirectional magnetic anisotropy due to the exchange interactionbetween the two layers. The second ferromagnetic material layer 35 whosemagnetization direction can be rotated comparatively easily is alsocalled a free layer or a recording layer. Incidentally, the secondferromagnetic material layer may be called the recording layer 35 in thefollowing description. The tunnel insulation film 34 plays the roles ofinterrupting the magnetic coupling between the recording layer 35 andthe magnetization fixation layer 33 and of passing a tunnel current. Abit line BL for connection between the MRAMs is formed on an upperinterlayer insulation layer 26. A top coat film 36 provided between thebit line BL and the recording layer 35 functions to prevent mutualdiffusion between the atoms constituting the bit line BL and the atomsconstituting the recording layer 35, to reduce the contact resistance,and to prevent the oxidation of the recording layer 35. In the figure,the reference numeral 37 denotes an extraction electrode connected tothe lower surface of the antiferromagnetic material layer 32.

Further, a write word line RWL is disposed on the lower side of thetunnel magnetoresistance device TMJ, with a lower interlayer insulationlayer 24 therebetween. Incidentally, the extension direction of thewrite word line RWL (first direction) and the extension direction of thebit line BL (second direction) are ordinarily orthogonal to each other.

On the other hand, the selection transistor TR is formed at a portion ofa silicon semiconductor substrate 10 surrounded by a device isolationregion 11, and is covered with an interlayer insulation layer 21. Asource/drain region 14B on one side is connected to an extractionelectrode 37 for the tunnel magnetoresistance device TMJ through acontact hole 22 including a tungsten plug, a landing pad portion 23, anda contact hole 25 including a tungsten plug. A source/drain region 14Aon the other side is connected to a sense line 16 through a tungstenplug 15. In the figure, reference numeral 12 denotes a gate electrode,and reference numeral 13 denotes a gate insulation film.

In the MRAM array, the MRAM is arranged at each of the intersections(overlapping regions) in the lattice composed of the bit lines BL andthe write word lines RWL.

In writing data into the MRAM configured as above, a current in thepositive or negative direction is passed through the bit line BL, whilea current in a fixed direction is passed through the write word lineRWL, and the composite magnetic field thus generated changes themagnetization direction of the second ferromagnetic material layer(recording layer 35), whereby “1” or “0” is recorded in the secondferromagnetic material layer (recording layer 35).

On the other hand, reading of data is conducted by setting the selectiontransistor TR into the ON state, passing a current through the bit lineBL, and detecting via the sense line 16 the change in the tunnel currentdue to the magnetoresistance effect. Where the magnetization directionsof the recording layer 35 and the magnetization fixation layer 33 areequal, a low resistance result is obtained (this state is made to be“0”, for example), and where the magnetization directions of therecording layer 35 and the magnetization fixation layer 33 areanti-parallel, a high resistance result is obtained (this state is madeto be “1”, for example).

In reading the data, suppression of the dispersion in the resistance ofthe recording layer 35 by maximizing the uniformity of the areas(projection areas) of the tunnel magnetoresistance devices TMJs leads toa reduction in the data reading dispersion, whereby the yield ofmanufacture is enhanced. One example of the distribution of resistanceof the recording layer 35 is shown in FIG. 19. By making the resistancevariation ratio as uniform as possible and suppressing the variancewidth (dispersion) of resistance, it is possible to obtain a largeroperation margin of the MRAM and to achieve a higher yield ofmanufacture. In other words, for the same operation margin on a designbasis, it is possible to obtain a larger signal voltage and ahigher-speed operation.

On the other hand, in writing the data, suppression of the variancewidth (dispersion) of the switching magnetic fields (H_(Switch)) of thetunnel magnetoresistance devices TMJs may be indispensable for obtaininga large-capacity memory.

FIG. 20 shows an asteroid curve of MRAM disclosed in U.S. Pat. No.6,081,445. Currents are passed through the bit line BL and the writeword line RWL, and, based on the composite magnetic field thusgenerated, data is written into the tunnel magnetoresistance device TMJconstituting the MRAM. The write current flowing through the bit line BLforms a magnetic field (H_(EA)) in the easy axis of magnetization of therecording layer 35, and the current flowing through the write word lineRWL forms a magnetic field (H_(HA)) in the hard axis of magnetization ofthe recording layer 35. Depending on the configuration of the MRAM,there may be the cases where the write current flowing through the bitline BL forms the magnetic field (H_(HA)) in the hard axis of therecording layer 35, and the current flowing through the write word lineRWL forms the magnetic field (H_(EA)) in the easy axis of the recordinglayer 35.

The asteroid curve shows a threshold for inversion of magnetizationdirection of the recording layer 35 due to the composite magnetic field(composition of magnetic field vectors of the magnetic field H_(HA) andthe magnetic field H_(EA) exerted on the recording layer 35), and, whena composite magnetic field corresponding to the outside (OUT₁, OUT₂) ofthe asteroid curve is generated, inversion of the magnetizationdirection of the recording layer 35 occurs, whereby data is written. Onthe other hand, when a composite magnetic field corresponding to theinside (IN) of the asteroid curve is generated, inversion of themagnetization direction of the recording layer 35 does not occur. Inaddition, to the MRAMs other than that at the intersection between thewrite word line RWL and the bit line BL through which the current flow,a magnetic field generated by the write word line RWL or bit line BLalone is applied, so that if the magnitude of this magnetic field is notless than the switching magnetic field (H_(Switch)) [the region (OUT₂)on the outside of the broken lines in FIG. 20], the magnetizationdirection of the recording layer 35 constituting the other MRAMs thanthat at the intersection would also be inverted. Therefore, only in thecase where the composite magnetic field is on the outside of theasteroid curve and in the region (OUT₁) on the inside of the brokenlines in FIG. 20, selective writing into the selected MRAM can beachieved.

More specifically, in writing the data, as has been described above,currents are passed through the bit line BL and the write word line RWLto generate a composite magnetic field; in this case, the magnitude ofthe composite magnetic field is set to be located slightly on theoutside of the asteroid curve, and about one half of the compositemagnetic field is generated by use of the bit line BL and the write wordline RWL. Incidentally, such a state as this is called a “half selected”state. By achieving such a “half selected” state, data is written intothe tunnel magnetoresistance device TMJ located at the intersectionbetween the bit line BL through which the current flows and the writeword line RWL through which the current flows. On the other hand, nodata is written into the tunnel magnetoresistance devices TMJs locatedat the intersections between the bit lines BLs through which the currentflows and the write word lines RWLs through which no current flows, orthe tunnel magnetoresistance devices TMJs located at the intersectionsbetween the bit lines BLs through which no current flows and the writeword lines RWLs through which current flows. Incidentally, such a tunnelmagnetoresistance device TMJ (into which no data is written) will bereferred to as a non-selected tunnel magnetoresistance device TMJ, forconvenience. (see U.S. Pat. No. 6,081,445, U.S. Patent Publications Nos.6,545,906 B1 and 6,633,498 B1, and S. S. Parkin et al, Physical ReviewLetters, 7 may, pp. 2304-2307 (1990))

SUMMARY OF THE INVENTION

However, though data is intrinsically not written into non-selectedtunnel magnetoresistance devices TMJs, data may be written into thenon-selected tunnel magnetoresistance devices TMJs in the case where thedispersion of the switching magnetic field (H_(Switch)) is large.Specifically, where the dispersion of the switching magnetic field(H_(Switch)) is large, the writing margin for the tunnelmagnetoresistance devices TMJs is so small that a large-capacity memorycannot be realized. Therefore, it is important to minimize thedispersion of the switching magnetic field (H_(Switch)), and thesuppression of the dispersion leads to an enlargement of the datawriting margin.

Meanwhile, the magnitude of the switching magnetic field (H_(Switch)) isdetermined principally by the shape anisotropy in plan-view shape of thetunnel magnetoresistance device TMJ (particularly, the plan-view shapeof the recording layer 35) and the magnetic anisotropy of the tunnelmagnetoresistance device TMJ. Therefore, the plan-view shape of thetunnel magnetoresistance device TMJ (particularly, the plan-view shapeof the recording layer 35) is a major factor in control of magneticcharacteristics and, hence, the operations of writing the data “0” and“1”. It has been known to set the plan-view shape of the tunnelmagnetoresistance device TMJ to one of the various plan-view shapesshown in FIGS. 22A to 22F, for reducing the dispersion of the switchingmagnetic field (H_(Switch)). However, even the adoption of suchplan-view shapes is yet unsatisfactory for reducing the dispersion ofthe switching magnetic field (H_(Switch)). In a broader sense, thisapproach is not satisfactory in terms of the data writing margin for themagnetoresistance devices.

Accordingly, there is a need for a nonvolatile magnetic memory deviceincluding magnetoresistance devices capable of reducing the dispersionof the switching magnetic field (H_(Switch)) of, for example, tunnelmagnetoresistance devices, or, in a broader sense, capable of providinga sufficient data writing margin, and for a photomask for use in alithography step for manufacturing such magnetoresistance devices.

According to first to eighth embodiments of the present invention, thereis provided a nonvolatile magnetic memory device including amagentoresistance device having a recording layer formed of aferromagnetic material for storing information by use of variation inresistance depending on the magnetization inversion state thereof.

In the nonvolatile magnetic memory device according to a firstembodiment of the present invention,

-   -   the plan-view shape of the recording layer is a pseudo-rhombic        shape;    -   at least two of the four sides constituting the pseudo-rhombic        shape each including a smooth curve having a central portion        curved toward the center of the pseudo-rhombic shape;    -   the easy axis of magnetization of the recording layer is        substantially parallel to the longer axis of the pseudo-rhombic        shape;    -   the hard axis of magnetization of the recording layer is        substantially parallel to the shorter axis of the pseudo-rhombic        shape; and    -   the sides constituting the plan-view shape of the recording        layer are smoothly connected to each other.

Here, the “pseudo-rhombic shape” means that the plan-view shape of therecording layer has the following shape, as viewed macroscopically. Letthe four sides be represented by side A, side B, side C, and side D inthis order counterclockwise, the four sides A, B, C, and D beapproximated by line segments, the length of the line segment opposed toside A be L_(a), the length of the line segment opposed to side B beL_(b), the length of the line segment opposed to side C be L_(c), andthe length of the line segment opposed to side D be L_(d), then theplan-view shape satisfies L_(a)=L_(b)=L_(c)=L_(d), or satisfiesL_(a)≈L_(b)≈L_(c)≈L_(d), or satisfies L_(a)=L_(b)≠L_(c)=L_(d), orsatisfies L_(a)≈L_(b)≠L_(c)≈l_(d). When the recording layer is viewedmicroscopically, at least two (at maximum, four) of the four sidesconstituting the plan-view shape of the recording layer each include acurve.

Here, in general, where a real variable function F(X) has a continuousdifferential coefficient at each point in an interval a<X<b, thefunction F(X) is said to be “smooth” or “differentiable” over theinterval. In addition, the expression “substantially parallel” meansthat two line segments or straight lines do not intersect each other, orthat their intersection angle is within the range of ±20°. Besides, theexpression “substantially orthogonal” means that two line segments orstraight lines orthogonally intersect each other, or that theirintersection angle is in the range of 90°±20°. Further, the expression“substantially line symmetric” includes the meaning of not only the casewhere when the recording layer is folded along the axis of symmetry, thetwo portions of the recording layer folded perfectly overlap each otherbut also the case where the two portions of the recording layer foldeddo not perfectly overlap each other because of dispersions in themanufacturing process of the recording layer. Besides, the “center”means the center of gravity of the shape. Hereinafter, also, theexpressions “smooth”, “substantially parallel”, “substantially linesymmetric” and “center” will be used in the meanings just mentioned.

In the nonvolatile magnetic memory device according to this embodiment,it is desirable the relationship 1.0<L_(L)/L_(S)≈10, preferably1.2≦L_(L)/L_(S)≦3.0, is satisfied, where the length of the longer axisof the pseudo-rhombic shape is 2L_(L), and the length of the shorteraxis of the shape is 2L_(S). In addition, it is desirable that therelationship 0.1≦r_(L)/L_(S)≦1.0, preferably 0.2≦r_(L)/L_(S)≦0.8, issatisfied, and the relationship 0.1≦r_(S)/L_(L)≦10, preferably0.2≦r_(S)/L_(L)≦5, is satisfied, where r_(L) is the radius of curvatureof the plan-view shape of the recording layer at the intersectionbetween the longer axis of the pseudo-rhombic shape and the plan-viewshape of the recording layer, and r_(S) is the radius of curvature ofthe plan-view shape of the recording layer at the intersection betweenthe shorter axis of the pseudo-rhombic shape and the plan-view shape ofthe recording layer.

In the nonvolatile magnetic memory device according to this embodiment,it is preferable that at least two points of inflection are present ineach of the sides each including a smooth curve having a central portionthereof curved.

In the nonvolatile magnetic memory device according to this embodimentincluding the above-mentioned properties, it is desirable that when thepseudo-rhombic shape is divided into two regions by the longer axis ofthe pseudo-rhombic shape, the two sides each including a smooth curvehaving a central portion thereof curved belong to one of the regions.

Alternatively, in the nonvolatile magnetic memory device according tothis embodiment including the above-mentioned properties, it isdesirable that the four sides each include a smooth curve having acentral portion thereof curved toward the center of the pseudo-rhombicshape.

In the nonvolatile magnetic memory device according to this embodimentincluding the above-mentioned properties, it is desirable that theplan-view shape of the recording layer is substantially line symmetricwith respect to the shorter axis of the pseudo-rhombic shape. Such aconfiguration includes the case where the two of the four sidesconstituting the pseudo-rhombic shape each include a smooth curve havinga central portion thereof curved toward the center of the pseudo-rhombicshape, and the case where all of the four sides constituting thepseudo-rhombic shape each include a smooth curve having a centralportion thereof curved toward the center of the pseudo-rhombic shape.Furthermore, it is desirable that the plan-view shape of the recordinglayer is substantially line symmetric with respect to the longer axis ofthe pseudo-rhombic shape.

In the nonvolatile magnetic memory device according to a secondembodiment of the present invention,

-   -   the plan-view shape of the recording layer includes four sides;    -   at least two of the four sides each include a smooth curve;    -   the plan-view shape of the recording layer is inscribed in a        virtual rhombus having a longer axis, and a shorter axis        orthogonally intersecting the longer axis at the bisecting point        of the longer axis, the longer axis being substantially parallel        to the easy axis of magnetization of the recording layer, and        the shorter axis being substantially parallel to the hard axis        of magnetization of the recording layer;    -   each of the sides each including the smooth curve contacts the        corresponding side of the virtual rhombus at at least two        points; and    -   the sides constituting the plan-view shape of the recording        layer are smoothly connected to each other.

Here, in the “virtual rhombus”, when the four sides of the virtualrhombus are represented by side A (length: L_(a)), side B (length:L_(b)), side C (length: L_(c)), and side D (length L_(d)) in this ordercounterclockwise, the virtual rhombus satisfies L_(a)=L_(b)=L_(c)=L_(d),or satisfies L_(a)≈L_(b)≈L_(c)≈L_(d), or satisfiesL_(a)=L_(b)≠L_(c)=L_(d), or satisfies L_(a)≈L_(b)≠L_(c)≈L_(d).

In the nonvolatile magnetic memory according to this embodiment of thepresent invention, it is desirable that the relationship1.0<L_(i-L)/L_(i-S)≦10, preferably 1.2≦L_(i-L)/L_(i-S)≦3.0, issatisfied, where the length of the longer axis is 2L_(i-L), and thelength of the shorter axis is 2L_(i-S). In addition, it is desirablethat the relationship 0.1≦r_(L)/L_(i-S)<1.0, preferably0.2≦r_(L)/L_(i-S)≦0.8, is satisfied and that the relationship0.1≦r_(S)/L_(i-L)≦10, preferably 0.2≦r_(S)/L_(i-L)≦5, is satisfied,where r_(L) is the radius of curvature of the plan-view shape of therecording layer at the intersection between the longer axis of thevirtual rhombic and the plan-view shape of the recording layer, andr_(S) is the radius of curvature of the plan-view shape of the recordinglayer at the intersection between the shorter axis of the virtualrhombic and the plan-view shape of the recording layer. Further, in aninterval 0<X<X₁ (described below) of the side including a smooth curve,it is desirable that the relationship 0<D_(MAX)≦X₁/2, preferablyX₁/30≦D_(MAX)≦X₁/3, is satisfied, where D_(MAX) is the maximum distancebetween the side including a smooth curve and the corresponding side ofthe virtual rhombic.

In the nonvolatile magnetic memory device according to this embodimentof the present invention, it is desirable that

-   -   when, in each of the sides constituting the plan-view shape of        the recording layer and each including the smooth curve,    -   (a) the point located closest to the shorter axis of the virtual        rhombus, of the at least two points of contact with the side of        the virtual rhombus is made to be the origin (0, 0) of a        Gaussian coordinate system,    -   (b) the point located closest to the longer axis of the virtual        rhombus, of the at least two points of contact with the side of        the virtual rhombus is made to be (X₁, 0) [where X₁>0],    -   (c) the intersection with the shorter axis of the virtual        rhombus is made to be (X_(S), Y_(S)) [where X_(S)<0, Y_(S)<0],    -   (d) the intersection with the longer axis of the virtual rhombus        is made to be (X_(L), Y_(L)) [where X_(L)>0, Y_(L)<0]; and    -   the side is represented by a real variable function F(X), and        the intersection of the longer axis and the shorter axis of the        virtual rhombus is located in the third quadrant or the fourth        quadrant; then    -   the real variable function F(X) has a continuous differential        coefficient at each point in an interval X_(S)<X<X_(L), and    -   the real variable function F(X) has at least two points of        inflection in an interval 0<X<X₁.

In the nonvolatile magnetic memory device according to this embodimentof the present invention including the above-mentioned properties, it isdesirable that the plan-view shape of the recording layer issubstantially line symmetric with respect to the shorter axis of thevirtual rhombus. Such a configuration includes the case where two of thefour sides constituting the plan-view shape of the recording layer eachinclude a smooth curve, and the case where all of the four sides eachinclude a smooth curve. Alternatively, it is desirable that the foursides of the plan-view shape of the recording layer each include asmooth curve, and that the plan-view shape of the recording layer issubstantially line symmetric with respect to the virtual rhombus, and issubstantially line symmetric with respect to the longer axis of thevirtual rhombus.

In the nonvolatile magnetic memory device according to a thirdembodiment of the present invention,

-   -   the plan-view shape of the recording layer includes a first        shape, and two projected portions oppositely projected from the        first shape;    -   the two projected portions are positioned on the projected        portion axis;    -   the axis of each of the projected portions passes through the        center of the first shape and orthogonally intersects the first        shape axis passing through the center of the first shape;    -   the first shape includes one shape selected from the group        including an ellipse, a flat oval, and a flat circle;    -   the projected portions each include one shape selected from the        group including a part of a circle, a part of an ellipse, a part        of a flat oval, and a part of a flat circle;    -   the easy axis of magnetization of the recording layer is        substantially parallel to the first shape axis;    -   the hard axis of magnetization of the recording layer is        substantially parallel to the projected portion axis;    -   the relationship L_(L)>L_(S) is satisfied, where 2L_(L) is the        length of the first shape along the first shape axis, and 2L_(S)        is the distance between the tip ends of the two projected        portions along the projected portion axis; and    -   the portion at which the visible outline of the first shape and        the visible outline of each side projected portion intersect        includes a smooth curve.

In the nonvolatile magnetic memory device according to this embodimentof the present invention, examples of the combination of (the firstshape, the projected portion) include (an ellipse, a part of a circle),(an ellipse, a part of an ellipse), (an ellipse, a part of a flat oval),(an ellipse, a part of a flat circle), (a flat oval, a part of acircle), (a flat oval, a part of an ellipse), (a flat oval, a part of aflat oval), (a flat oval, a part of a flat circle), (a flat circle, apart of a circle), (a flat circle, a part of an ellipse), (a flatcircle, a part of a flat oval), (a flat circle, a part of a flatcircle).

In the nonvolatile magnetic memory device according to this embodimentof the present invention, it is desirable that the relationship1.0<L_(L)/L_(S)<10, preferably 1.2≦L_(L)/L_(S)≦3.0, is satisfied. Inaddition, it is desirable that the relationship 0.1<r_(L)/L_(S)≦1.0,preferably 0.2<r_(L)/L_(S)≦0.8, is satisfied, and the relationship0.1≦r_(S)/L_(L)≦10, preferably 0.2≦r_(S)/L_(L)≦5, is satisfied, wherer_(L) is the radius of curvature of the plan-view shape of the recordinglayer as the intersection between the first shape axis and the plan-viewshape of the recording layer, and r_(S) is the radius of curvature ofthe plan-view shape of the recording layer at the intersection betweenthe projected portion axis and the plan-view shape of the recordinglayer.

In the nonvolatile magnetic memory device according to this embodimentof the present invention, the plan-view shape of the recording layer maybe substantially line symmetric with respect to the projected portionaxis. Incidentally, such a configuration includes the case where the twoprojected portions are substantially line symmetric with respect to thefirst shape axis, and the case where the two projected portions are notline symmetric. It is desirable that the plan-view shape of therecording layer is substantially line symmetric with respect to theprojected portion axis, and is line symmetric with respect to the firstshape axis.

In the nonvolatile magnetic memory device according to a fourthembodiment of the present invention,

-   -   the plan-view shape of the recording layer is a superposed shape        in which a first shape and a second shape having a center        coinciding with the center of the first shape are superposed on        each other so that the second shape is projected from the first        shape at two positions;    -   the first shape axis passing through the center of the first        shape and the second shape axis passing through the center of        the second shape orthogonally intersect each other;    -   the first shape includes one shape selected from the group        including an ellipse, a flat oval, and a flat circle;    -   the second shape includes one shape selected from the group        including a circle, an ellipse, a flat oval, and a flat circle;    -   the easy axis of magnetization of the recording layer is        substantially parallel to the first shape axis;    -   the hard axis of magnetization of the recording layer is        substantially parallel to the second shape axis;    -   the relationship L_(L)>L_(S) is satisfied, where 2L_(L) is the        length of the first shape along the first shape axis, and 2L_(S)        is the length of the second shape along the second shape axis;        and    -   the portion at which the visible outline of the first shape and        the visible outline of the second shape intersect each other        includes a smooth curve.

In the nonvolatile magnetic memory device according to this embodimentof the present invention, examples of the combination of (the firstshape, the second shape) include (an ellipse, a circle), (an ellipse, anellipse), (an ellipse, a flat oval), (an ellipse, a flat circle), (aflat oval, a circle), (a flat oval, an ellipse), (a flat oval, a flatoval), (a flat oval, a flat circle), (a flat circle, a circle), (a flatcircle, an ellipse), (a flat circle, a flat oval), and (a flat circle, aflat circle).

In the nonvolatile magnetic memory device according to this embodimentof the present invention, it is desirable that the relationship1.0<L_(L)/L_(S)≦10, preferably 1.2≦L_(L)/L_(S)≦3.0, is satisfied. Inaddition, it is desirable that the relationship 0.1≦r_(L)/L_(S)≦1.0,preferably 0.2≦r_(L)/L_(S)≦0.8, is satisfied, and the relationship0.1≦r_(S)/L_(L)≦10, preferably 0.2≦r_(S)/L_(L)≦5, is satisfied, wherer_(L) is the radius of curvature of the plan-view shape of the recordinglayer at the intersection between the first shape axis and the plan-viewshape of the recording layer, and r_(S) is the radius of curvature ofthe plan-view shape of the recording layer at the intersection betweenthe second shape axis and an the plan-view shape of the recording layer.

In the nonvolatile magnetic memory device according to this embodimentof the present invention, the plan-view shape of the recording layer maybe substantially line symmetric with respect to the second shape axis.Such a configuration includes the case where the two projected regionsof the second shape are substantially line symmetric with respect to thefirst shape axis, and the case where the two projected regions are notline symmetric. It is desirable that the plan-view shape of therecording layer is substantially line symmetric with respect to thesecond shape axis and is substantially line symmetric with respect tothe first shape axis.

In the nonvolatile magnetic memory device according to a fifthembodiment of the present invention,

-   -   the plan-view shape of the recording layer includes a pseudo        isosceles triangular shape;    -   the oblique lines of the pseudo isosceles triangular shape each        include a smooth curve having a central portion thereof curved        toward the center of the pseudo isosceles triangular shape;    -   the length of the imaginary base of the pseudo isosceles        triangular shape is greater than the virtual height of the        pseudo isosceles triangular shape;    -   the easy axis of magnetization of the recording layer is        substantially parallel to the base of the pseudo isosceles        triangular shape;    -   the hard axis of magnetization of the recording layer is        substantially orthogonal to the base of the pseudo isosceles        triangular shape; and    -   the sides constituting the plan-view shape of the recording        layer are smoothly connected to each other.

Here, the “pseudo isosceles triangular shape” means that the plan-viewshape of the recording layer has the following shape, as viewedmacroscopically. Let the two oblique lines A and B be approximated byline segments, let the length of the line segment opposed to the obliqueline A be L_(a), and let the length of the line segment opposed to theoblique line B be L_(b), then the shape satisfies the relationshipL_(a)=L_(b), or satisfies the relationship L_(a)≈L_(b). When therecording layer is viewed microscopically, the two oblique linesconstituting the plan-view shape of the recording layer each include acurve.

In the nonvolatile magnetic memory device according to this embodimentof the present invention, the length of the imaginary base of the pseudoisosceles triangular shape is represented by 2L_(B), the virtual heightis represented by H, the average radius of curvature of the plan-viewshape of the recording layer at the portion where the oblique line andthe base line of the pseudo isosceles triangular shape are smoothlyconnected to each other is represented by r_(L), and the radius ofcurvature of the plan-view shape of the recording layer at theintersection between the two oblique lines of the pseudo isoscelestriangular shape is represented by r_(S). Here, the intersection betweenthe two oblique lines of the pseudo isosceles triangular shape means thepoint at which the perpendicular bisector of the imaginary baseintersects the curve obtained by connecting the two oblique lines of thepseudo isosceles triangular shape into one line. In addition, theimaginary base of the pseudo isosceles triangular shape means animaginary line which, when the base of the pseudo isosceles triangularshape is approximated by a straight line (this straight line is calledbase approximation straight line), is parallel to the base approximationstraight line, which passes through a point being located on the side ofthe intersection between the two oblique lines of the pseudo isoscelestriangular shape and being spaced from the base approximation straightline by a distance r_(L). Further, the length 2L_(B) of the imaginarybase is defined as the distance between the intersections of theimaginary base with the plan-view shape of the recording layer at theportions where the oblique lines and the base of the pseudo isoscelestriangular shape are smoothly connected. Besides, the virtual height His defined as the distance from the intersection between the two obliquelines of the pseudo isosceles triangular shape to the imaginary base. Inthis case, it is desirable that the relationship 1.0<L_(B)/H≦10,preferably 1.2≦L_(B)/H≦3.0, is satisfied. In addition, it is desirablethat the relationship 0.1≦r_(L)/H≦1.0, preferably 0.2≦r_(L)/H≦0.8, issatisfied, and it is desirable that the relationship 0.1≦r_(S)/L_(B)≦10,preferably 0.2≦r_(S)/L_(B)≦5 is satisfied.

In the nonvolatile magnetic memory device according to this embodimentof the present invention, it is preferable that at least two points ofinflection are present in the oblique line of the pseudo isoscelestriangular shape. It is desirable that the plan-view shape of therecording layer is substantially line symmetric with respect to theperpendicular bisector of the imaginary base of the pseudo isoscelestriangular shape.

In the nonvolatile magnetic memory device according to a sixthembodiment of the present invention,

-   -   the plan-view shape of the recording layer includes three sides;    -   at least two of the three sides each include a smooth curve;    -   the plan-view shape of the recording layer is inscribed in a        virtual isosceles triangle in which the length of the imaginary        base is 2L_(i-B), the virtual height is H_(i) [where        H_(i)<L_(i-B)], the base is substantially parallel to the easy        axis of magnetization of the recording layer, and the        perpendicular to the base is substantially parallel to the hard        axis of magnetization of the recording layer;    -   each of the sides each including the smooth curve contacts an        oblique line of the virtual isosceles triangle at at least two        points; and    -   the sides constituting the plan-view shape of the recording        layer are smoothly connected to each other.

In the nonvolatile magnetic memory device according to this embodimentof the present invention, the imaginary base of the virtual isoscelestriangle means an imaginary line being parallel to the base of thevirtual isosceles triangle and passing a point which is located on theside of the intersection between the two oblique lines of the virtualisosceles triangle and which is spaced from the base of the virtualisosceles triangle by a distance r_(L), where r_(L) is the averageradius of curvature of the plan-view shape of the recording layer at theportion where a side constituting the plan-view shape of the recordinglayer and corresponding to the base of the virtual isosceles triangle issmoothly connected to a side constituting the plan-view shape of therecording layer and corresponding to the oblique line of the virtualisosceles triangle. In addition, the length 2L_(i-B) of the imaginarybase is defined as the distance between the imaginary base and theintersection of the two oblique lines of the virtual isosceles triangle.Besides, the virtual height H_(i) is defined as the distance from theintersection of the two oblique lines of the virtual isosceles triangleto the imaginary base. In the nonvolatile magnetic memory deviceaccording to this embodiment of the present invention, it is desirablethat the relationship 1.0<L_(i-B)/H_(i)≦10, preferably1.2≦L_(i-B)/H_(i)≦3.0, is satisfied. In addition, it is desirable thatthe relationship 0.1≦r_(L)/H_(i)≦1.0, preferably 0.2≦r_(L)/H_(i)≦0.8, issatisfied, and it is desirable that the relationship0.1≦r_(S)/L_(i-B)≦10, preferably 0.2≦r_(S)/L_(i-B)≦5, is satisfied,where r_(S) is the radius of curvature of the plan-view shape of therecording layer at the intersection between the plan-view shape of therecording layer and the bisector of the angle formed at the intersectionof the two oblique lines of the virtual isosceles triangle. Further, inthe interval 0<X<X₁ (described below) of the side including a smoothcurve, let the maximum distance between the side including the smoothcurve and the corresponding oblique side of the virtual isoscelestriangle be D_(MAX), then it is desirable that the relationship0<D_(MAX)≦X₁/2, preferably X₁/30≦D_(MAX)≦X₁/3, is satisfied.

In the nonvolatile magnetic memory device according to this embodimentof the present invention, it is desirable that

-   -   when, in each of the sides each including the smooth curve and        constituting the plan-view shape of the recording layer,    -   (a) the point closest to the intersection between the two        oblique lines of the virtual isosceles triangle, of at least two        points of contact with the oblique line, is made to be the        origin (0, 0) of a Gaussian coordinate system,    -   (b) the point closest to the intersection between the oblique        line and the imaginary base of the virtual isosceles triangle,        of at least two points of contact with the oblique line, is made        to be (X₁, 0) [where X₁>0],    -   (c) the intersection with the perpendicular bisector of the base        of the virtual isosceles triangle is made to be (X_(S), Y_(S))        [where X_(S)<0, Y_(S)<0],    -   (d) the intersection with the imaginary base of the virtual        isosceles triangle is made to be (X_(L), Y_(L)) [where X_(L)>0,        Y_(L)<0]; and    -   the side is represented by a real variable function F(X), and        the intersection between the perpendicular bisector of the base        of the virtual isosceles triangle and the base of the virtual        isosceles triangle is located in the third quadrant or the        fourth quadrant;    -   the real variable function F(X) has a continuous differential        coefficient at each point in an interval X_(S)<X<X_(L), and    -   the real variable function F(X) has at least two points of        inflection in an interval 0<X<X₁.

In the nonvolatile magnetic memory device according to this embodimentof the present invention including the above-mentioned preferableconfiguration, it is desirable that the plan-view shape of the recordinglayer is substantially line symmetric with respect to the perpendicularbisector of the base of the virtual isosceles triangle.

In the nonvolatile magnetic memory device according to a seventhembodiment of the present invention,

-   -   the plan-view shape of the recording layer includes a first        shape, and a projected portion projected from the first shape;    -   the projected portion is located on the projected portion axis;    -   the projected portion axis passes through the center of the        first shape, and orthogonally intersects the first shape axis        passing through the center of the first shape;    -   the first shape has one shape selected from the group including        an ellipse, a flat oval, and a flat circle;    -   the projected portion has one shape selected from the group        including a part of a circle, a part of an ellipse, a part of a        flat oval, and a part of a flat circle;    -   the easy axis of magnetization of the recording layer is        substantially parallel to the first shape axis;    -   the hard axis of magnetization of the recording layer is        substantially parallel to the projected portion axis;    -   the relationship L_(L)>L_(S) is satisfied, where 2L_(L) is the        length of the first shape along the first shape axis, and L_(S)        is the distance from a tip end portion of the projected portion        to the center of the first shape along the projected portion        axis; and    -   the portion at which the visible outline of the first shape and        the visible outline of the projected portion intersect includes        a smooth curve.

In the nonvolatile magnetic memory device according to this embodimentof the present invention, examples of the combination of (the firstshape, the projected portion) include (an ellipse, a part of a circle),(an ellipse, a part of an ellipse), (an ellipse, a part of a flat oval),(an ellipse, a part of a flat circle), (a flat oval, a part of acircle), (a flat oval, a part of an ellipse), (a flat oval, a part of aflat oval), (a flat oval, a part of a flat circle), (a flat circle, apart of a circle), (a flat circle, a part of an ellipse), (a flatcircle, a part of a flat oval), and (a flat circle, a part of a flatcircle).

In the nonvolatile magnetic memory device according to this embodimentof the present invention, it is desirable that the relationship1.0<L_(L)/L_(S)≦10, preferably 1.2≦L_(L)/L_(S)≦3.0, is satisfied. Inaddition, it is desirable that the relationship 0.1≦r_(L)/L_(S)≦1.0,preferably 0.2≦r_(L)/L_(S)≦0.8, is satisfied, and it is desirable thatthe relationship 0.1≦r_(S)/L_(L)≦10, preferably 0.2≦r_(S)/L_(L)≦5, issatisfied, where r_(L) is the radius of curvature of the plan-view shapeof the recording layer at the intersection between the first shape axisand the plan-view shape of the recording layer, and r_(S) is the radiusof curvature of the plan-view shape of the recording layer at theintersection between the projected portion axis and the plan-view shapeof the recording layer.

In the nonvolatile magnetic memory device according to this embodimentof the present invention, it is desirable that the plan-view shape ofthe recording layer is substantially line symmetric with respect to theprojected portion axis.

In the nonvolatile magnetic memory device according to an eighthembodiment of the present invention,

-   -   the plan-view shape of the recording layer is a superposed shape        in which a first shape and a second shape are superposed on each        other so that the second shape is projected from the first shape        at one position;    -   the second shape is located on the second shape axis;    -   the second shape axis passes through the center of the first        shape, and orthogonally intersects the first shape axis passing        through the center of the first shape;    -   the first shape has one shape selected from the group including        an ellipse, a flat oval, and a flat circle;    -   the second shape has one shape selected from the group including        a circle, an ellipse, a flat oval, and a flat circle;    -   the easy axis of magnetization of the recording layer is        substantially parallel to the first shape axis;    -   the hard axis of magnetization of the recording layer is        substantially parallel to the second shape axis;    -   the relationship L_(L)>L_(S) is satisfied, where 2L_(L) is the        length of the first shape along the first shape axis, and L_(S)        is the distance from a tip end portion of the second shape to        the center of the first shape along the second shape axis; and    -   the portion at which the visible outline of the first shape and        the visible outline of the second shape intersect includes a        smooth curve.

In the nonvolatile magnetic memory device according to this embodimentof the present invention, examples of the combination of (the firstshape, the second shape) include (an ellipse, a circle), (an ellipse, anellipse), (an ellipse, a flat oval), (an ellipse, a flat circle), (aflat oval, a circle, (a flat oval, an ellipse), (a flat oval, a flatoval), (a flat oval, a flat circle), (a flat circle, a circle), (a flatcircle, an ellipse), (a flat circle, a flat oval), and (a flat circle, aflat circle).

In the nonvolatile magnetic memory device according to this embodimentof the present invention, it is desirable that the relationship1.0<L_(L)/L_(S)≦10, preferably 1.2≦L_(L)/L_(S)≦3.0, is satisfied. Inaddition, it is desirable that the relationship 0.1≦r_(L)/L_(S)≦1.0,preferably 0.2≦r_(L)/L_(S)≦0.8, is satisfied, and it is desirable that0.1≦r_(S)/L_(L)≦10, preferably 0.2≦r_(S)/L_(L)≦5, is satisfied, wherer_(L) is the radius of curvature of the plan-view shape of the recordinglayer at the intersection between the first shape axis and the plan-viewshape of the recording layer, and r_(S) is the radius of curvature ofthe plan-view shape of the recording layer at the intersection betweenthe second shape axis and the plan-view shape of the recording layer.

In the nonvolatile magnetic memory device according to this embodimentof the present invention, it is desirable that the plan-view shape ofthe recording layer is substantially line symmetric with respect to thesecond shape axis.

The plan-view shapes of the recording layers in the nonvolatile magneticmemory devices according to the first to eighth embodiments of thepresent invention will be referred to as the Saturn type, forconvenience.

In the nonvolatile magnetic memory devices according to the first toeighth embodiments of the present invention including the various formsand configurations, specifically, examples of the nonvolatile magneticmemory device include a nonvolatile magnetic memory device having atunnel magnetoresistance device using the TMR effect, and a nonvolatilemagnetic memory device having a spin implantation type magnetoresistancedevice applying the inversion of magnetization by spin implantation.

In the nonvolatile magnetic memory device having a tunnelmagnetoresistance device, specifically, the magnetoresistance device isa tunnel magnetoresistance device having a laminate structure includinga first ferromagnetic material layer, a tunnel insulation film, and asecond ferromagnetic material layer, in this order from the lower side;in this case, the recording layer (referred to also as a free layer)constitutes the second ferromagnetic material layer.

Further, the nonvolatile magnetic memory device may have a structureincluding first and second wirings. The first wiring extending in afirst direction, including a conductor layer, and being electricallyinsulated from the first ferromagnetic material layer is provided on thelower side of the first ferromagnetic material layer, with a lowerinterlayer insulation layer therebetween. The second wiring extending ina second direction different from the first direction, including aconductor layer, and being electrically connected to the secondferromagnetic material layer or electrically isolated from the secondferromagnetic material layer is provided on the upper side of the secondferromagnetic material layer, with an upper interlayer insulation layertherebetween.

Furthermore, the nonvolatile magnetic memory device may have a structurein which: a selection transistor including a field effect transistor isprovided on the lower side of the first wiring, with an interlayerinsulation layer therebetween; and the first ferromagnetic materiallayer is electrically connected to one of source/drain regions of theselection transistor.

In other words, specifically but not limitatively, the nonvolatilemagnetic memory device having a tunnel magnetoresistance layer mayinclude:

-   -   a selection transistor provided on a semiconductor substrate;    -   an interlayer insulation layer covering the selection        transistor;    -   a lower interlayer insulation layer; and    -   an upper interlayer insulation layer.

A write word line is formed on the lower interlayer insulation layer,

-   -   the lower interlayer insulation layer covers the write word line        and the interlayer insulation layer,    -   the first ferromagnetic material layer is formed on the lower        interlayer insulation layer,    -   the upper interlayer insulation layer covers the tunnel        magnetoresistance device and the lower interlayer insulation        layer,    -   an extension portion of the first ferromagnetic material layer        or an extraction electrode extending on the upper side of the        lower interlayer insulation layer from the first ferromagnetic        material layer is electrically connected to the selection        transistor through a contact hole (or a contact hole and a        landing pad portion) provided in the lower interlayer insulation        layer and the interlayer insulation layer, and    -   a bit line is formed on the upper interlayer insulation layer.

In accordance with one embodiment of the present invention, there isprovided a photomask for use in a lithography step for forming arecording layer constituting a magnetoresistance device in a nonvolatilemagnetic memory device, the recording layer including:

(A) a ferromagnetic material for storing information by use of variationin resistance depending on the magnetization inversion state thereof,

-   -   (B) the plan-view shape of the recording layer being a        pseudo-rhombic shape,    -   (C) the sides constituting the pseudo-rhombic shape each        including a smooth curve having a central portion thereof curved        toward the center of the pseudo-rhombic shape,    -   (D) the easy axis of magnetization of the recording layer being        substantially parallel to the longer axis of the pseudo-rhombic        shape,    -   (E) the hard axis of magnetization of the recording layer being        substantially parallel to the shorter axis of the pseudo-rhombic        shape, and    -   (F) the sides being smoothly connected to each other.

The photomask is provided with a pattern including a first shape and asecond shape, in which

-   -   the first shape and the second shape having a center coinciding        with the center of the first shape are superposed on each other        so that the second shape is projected from the first shape at        two positions;    -   the first shape axis passing through the center of the first        shape and the second shape axis passing through the center of        the second shape orthogonally intersect each other;    -   the first shape has one shape selected from the group including        a regular polygon, an ellipse, a flat oval, and a flat circle of        which the length along the first shape axis substantially        parallel to the easy axis is 2L_(p-1L), and the length along the        direction perpendicular to the first shape axis is        2L_(p-1S)[where L_(p-1S)<L_(p-1L)]; and    -   the second shape has one shape selected from the group including        a regular polygon, a circle, an ellipse, a flat oval, and a flat        circle of which the length along the second shape axis        substantially parallel to the hard axis is 2L_(p-2L) [where        L_(p-1S)<L_(p-2L)<L_(p-1L)], and the length along the direction        perpendicular to the second shape axis is 2L_(p-2S) [where        L_(p-2S)<L_(p-1L].)

Incidentally, while the second shape is projected from the first shapeat two positions, the shape of one of the projected regions of thesecond shape projected from the first shape and the shape of the otherof the projected regions of the second shape projected from the firstshape may be the same or different. Where the shapes of the projectedregions are the same, the plan-view shape of the recording layer is, forexample, substantially line symmetric with respect to the shorter axisof the pseudo-rhombic shape, and is substantially line symmetric withrespect also to the longer axis of the pseudo-rhombic shape. On theother hand, where the shapes of the projected regions are different, theplan-view shape of the recording layer is, for example, substantiallyline symmetric with respect only to the shorter axis of thepseudo-rhombic shape.

In accordance with another embodiment of the present invention, there isprovided a photomask for use in a lithography step for forming arecording layer constituting a magnetoresistance device in a nonvolatilemagnetic memory device, the recording layer including:

-   -   (A) a ferromagnetic material for storing information by use of        variation in resistance depending on the magnetization inversion        state thereof;    -   (B) the plan-view shape of the recording layer being a pseudo        isosceles triangular shape;    -   (C) the oblique lines of the pseudo isosceles triangular shape        each including a smooth curve having a central portion thereof        curved toward the center of the pseudo isosceles triangular        shape;    -   (D) the easy axis of magnetization of the recording layer being        substantially parallel to the base of the pseudo isosceles        triangular shape;    -   (E) the hard axis of magnetization of the recording layer being        substantially orthogonal to the base of the pseudo isosceles        triangular shape; and    -   (F) the sides of the plan-view shape being smoothly connected to        each other.

The photomask is provided with a pattern including a first shape and asecond shape, in which

-   -   the first shape and the second shape are superposed on each        other so that the second shape is projected from the first shape        at one position;    -   the second shape is located on the second shape axis;    -   the second shape axis passes through the center of the first        shape, and orthogonally intersects the first shape axis passing        through the center of the first shape;    -   the first shape has one shape selected from the group including        a regular polygon, an ellipse, a flat oval, and a flat circle of        which the length along the first shape axis substantially        parallel to the easy axis is 2L_(p-1L), and the length along the        direction passing through the center of the first shape and        being perpendicular to the first shape axis is 2L_(p-1S)[where        L_(p-1S)<L_(p-1L)]; and    -   the second shape has one shape selected from the group including        a regular polygon, a circle, an ellipse, a flat oval, and a flat        circle of which the distance from a tip end portion of the        second shape to the center of the first shape along the second        shape axis substantially parallel to the hard axis is L_(p-2L)        [where L_(p-1S)<L_(p-2L)<L_(p-1L)], and the length along the        direction passing through the center of the first shape and        being perpendicular to the second shape axis is 2L_(p-2S) [where        L_(p-2S)<L_(p-1L].)

In the photomask according to the one embodiment or another embodimentof the present invention, examples of the combination of (the firstshape, the second shape) include (a regular polygon, a regular polygon),(a regular polygon, a circle), (a regular polygon, an ellipse), (aregular polygon, a flat oval), (a regular polygon, a flat circle), (anellipse, a regular polygon), (an ellipse, a circle), (an ellipse, anellipse), (an ellipse, a flat oval), (an ellipse, a flat circle), (aflat oval, a regular polygon), (a flat oval, a circle), (a flat oval, anellipse), (a flat oval, a flat oval), (a flat oval, a flat circle), (aflat circle, a regular polygon), (a flat circle, a circle), (a flatcircle, an ellipse), (a flat circle, a flat oval), and (a flat circle, aflat circle).

When a resist material formed on a wafer is provided with a pattern byexposure light, that which is used for reduction projection may becalled a reticule, and that which is used for one-to-one projection maybe called a mask. Alternatively, that which corresponds to an originalmay be called a reticule, and that which is duplicated from the reticulemay be called a mask. Herein, the reticules and masks in these varioussenses are generically called photomask.

In the photomask according to the one embodiment or another embodimentof the present invention, the number of the second shape(s) is notlimited to one, and two or more second shapes may be used in combinationwith the first shape.

In the first shape, the second shape or the shape of the projectedportion in the nonvolatile magnetic memory device according to thethird, fourth, seventh or eighth embodiment of the present invention orthe photomask according to the one embodiment or another embodiment ofthe present invention, the flat oval means a figure formed bycombination of two semi-circles and two line segments. In addition, theflat circle means a figure obtained by flattening a circle in onedirection. Further, the regular polygon constituting the first shapeincludes rectangles, regular polygons having five or more vertices,rounded-vertex rectangles, and rounded-vertex regular polygons havingfive or more vertices, while the regular polygon constituting the secondshape includes squares, rectangles, regular polygons having five or morevertices, rounded-vertex squares, rounded-vertex rectangles, androunded-vertex regular polygons having five or more vertices.Incidentally, the shapes in question are not limited to circles andellipses but may include parabolas and hyperbolas; in other words, theshapes may be figures which can be represented by quadratic orhigher-order functions. Further, the shapes include combinations ofellipses with line segments, combinations of parabolas with linesegments, and combinations of hyperbolas with line segments. Morebroadly, the shapes may include combinations of quadratic functions withlinear functions, and combinations of third-order or higher-orderfunctions with linear functions.

In addition, the smooth curve portion obtained by curving a centralportion of a side constituting a pseudo-rhombic shape in the nonvolatilemagnetic memory device according to the first embodiment of the presentinvention, the smooth curve portion obtained by curving a centralportion of an oblique line constituting the pseudo isosceles triangularshape in the nonvolatile magnetic memory device according to the fifthembodiment of the present invention, the central portion of a sidehaving a smooth curve in the nonvolatile magnetic memory deviceaccording to the second or sixth embodiment of the present invention,the smooth curve constituting the portion where the visible outline ofthe first shape and the visible outline of the projected portionintersect in the nonvolatile magnetic memory device according to thethird or seventh embodiment of the present invention, and the smoothcurve constituting the portion where the visible outline of the firstshape and the visible outline of the second shape intersect in thenonvolatile magnetic memory device according to the fourth or eighthembodiment of the present invention, may be provided with smoothrecessed and projected portions.

Where the nonvolatile magnetic memory device includes a tunnelmagnetoresistance device using the TMR effect and having theabove-mentioned structure, the first ferromagnetic material layer morespecifically has, for example, a two-layer structure composed of anantiferromagnetic material layer and a ferromagnetic material layer(also called the anchoring layer or magnetization fixation layer),whereby a strong unidirectional magnetic anisotropy can be provided bythe exchange interaction between the two layers. Incidentally, themagnetization fixation layer makes contact with the tunnel insulationlayer. More specifically, the magnetization fixation layer may have, forexample, a multilayer structure (e.g., ferromagnetic materiallayer/metallic layer/ferromagnetic material layer) having an SAF(Synthetic Antiferromagnet) coupling. The SAF coupling is reported, forexample, in S. S. Parkin et al, Physical Review Letters, 7 May, pp.2304-2307 (1990). In the recording layer (second ferromagnetic materiallayer or free layer), the magnetization direction is rotatedcomparatively easily. The tunnel insulation film plays the roles ofinterrupting the magnetic coupling between the recording layer (secondferromagnetic material layer or free layer) and the magnetizationfixation layer and passing a tunnel current.

The ferromagnetic material layer (anchoring layer, magnetizationfixation layer) and the second ferromagnetic material layer (recordinglayer, free layer) may include a ferromagnetic material composed of atransition metal magnetic element, specifically, nickel (Ni), iron (Fe)or cobalt (Co), or may include a ferromagnetic material composed mainlyof an alloy of these metals (e.g., Co—Fe, Co—Fe—Ni, Ni—Fe, or the like).In addition, a so-called half-metallic ferromagnetic material and anamorphous ferromagnetic material such as CoFe—B may also be used.Examples of the material constituting the antiferromagnetic materiallayer include iron-manganese alloy, nickel-manganese alloy,platinum-manganese alloy, iridium-manganese alloy, rhodium-manganesealloy, cobalt oxide, and nickel oxide. These layers can be formed, forexample, by a physical vapor deposition process (PVD process)exemplified by sputtering process, ion beam build-up process, and vacuumevaporation process.

Examples of the insulation material constituting the tunnel insulationfilm include aluminum oxide (AlO_(x)), aluminum nitride (AlN), magnesiumoxide (MgO), magnesium nitride, silicon oxide, and silicon nitride, andfurther include Ge, NiO, CdO_(x), HfO₂, Ta₂O₅, BN, and ZnS. The tunnelinsulation film can be obtained, for example, by a method in which ametallic film formed by the sputtering process is oxidized or nitrided.More specifically, where aluminum oxide (AlO_(x)) is used as theinsulation material constituting the tunnel insulation film, examples ofthe method usable include a method in which aluminum formed by thesputtering process is oxidized in air, a method in which aluminum formedby the sputtering process is subjected to plasma oxidation in air, amethod in which aluminum formed by the sputtering process is oxidized byuse of an IPC plasma, a method in which aluminum formed by thesputtering process is subjected to spontaneous oxidation in oxygen, amethod in which aluminum formed by the sputtering process is oxidized byuse of oxygen radicals, a method in which aluminum formed by thesputtering process is subjected to spontaneous oxidation in oxygen whileirradiating with UV rays, a method in which a film of aluminum is formedby the reactive sputtering process, and a method in which a film ofaluminum oxide is formed by the sputtering process. Alternatively, thetunnel insulation film may be formed by the ALD (Atomic LayerDeposition) process.

The patterning of the laminate structure can be conducted, for example,by the reactive ion etching (RIE) process or the ion milling process(ion beam etching process). In some cases, the patterning can beconducted by the so-called lift-off process.

The write word line and the bit line may be formed, for example, ofaluminum, an aluminum-based alloy (e.g., Al—Cu), or copper (Cu), and canbe formed, for example, a PVD process exemplified by the sputteringprocess.

The contact hole may be formed of polysilicon doped with an impurity ora high-melting-temperature metal or metal silicide such as tungsten, Ti,Pt, Pd, Cu, TiW, TiNW, WSi₂, MoSi₂, etc., and can be formed by thechemical vapor deposition process (CVD process) or a PVD processexemplified by the sputtering process.

The selection transistor may be composed, for example, of a known MISFETor MOSFET.

Examples of the materials for constituting the interlayer insulationlayer, the lower interlayer insulation layer and the upper interlayerinsulation layer include silicon oxide (SiO₂), silicon nitride (SiN)SiON, SOG, NSG, PBSG, PSG, BSG, and LTO.

The plan-view shape of the recording layer in the nonvolatile magneticmemory devices according to the first to eighth embodiments of thepresent invention is made to be of the Saturn type, whereby thedispersion of the switching magnetic field H_(Switch) can be reduced,though the reason has not been elucidated. Particularly, even where themagnetoresistance device is damaged due to the dispersion in thelithography step, the processing dispersion in the case of adopting anetching process such as the RIE process and the ion milling process, oretching or an after-treatment (e.g., cleaning treatment in the case ofusing a chlorine-based gas for etching), the dispersion of the switchingmagnetic field H_(Switch) can be largely reduced. As a result, anasteroid characteristic with a large writing operation window, forexample, can be obtained, so that it is possible to suppress thedispersions between the nonvolatile magnetic memory devices, and torealize a nonvolatile magnetic memory device which is high inperformance and the degree of integration.

In the photomask according to the one embodiment or another embodimentof the present invention, the pattern formed in the photomask includes acombination of the first shape and the second shape, the designing ofthe pattern to be formed in the photomask can be carried out with a highdegree of freedom, for obtaining the recording layer having a desiredplan-view shape. What kind of pseudo-rhombic shape or pseudo isoscelestriangular shape can be obtained depending on the combination of thesize and shape of the first shape with the size and shape of the secondshape can be determined and evaluated by conducting a variety ofsimulations or by actually forming a pattern in a photomask andpatterning the recording layer on the basis of the photomask.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plan view of a recording layer in a nonvolatilemagnetic memory device in Example 1 as the nonvolatile magnetic memorydevice according to the first embodiment of the present invention;

FIG. 2 is a schematic plan view of a recording layer in a nonvolatilemagnetic memory device in Example 1 as the nonvolatile magnetic memorydevice according to the second embodiment of the present invention;

FIG. 3 is a schematic plan view of a recording layer in a nonvolatilemagnetic memory device in Example 1 as the nonvolatile magnetic memorydevice according to the third embodiment of the present invention;

FIG. 4 is a schematic plan view of a recording layer in a nonvolatilemagnetic memory device in Example 1 as the nonvolatile magnetic memorydevice according to the fourth embodiment of the present invention;

FIG. 5 shows an electron microphotograph of the plan-view of therecording layer provided in the nonvolatile magnetic memory device inExample 1, and an example of minor loop waveform;

FIG. 6 is a schematic partly sectional view of the nonvolatile magneticmemory device of the TMR type in Example 1;

FIGS. 7A to 7C are schematic partly sectional views of an interlayerinsulation layer and the like, for illustrating a method ofmanufacturing the nonvolatile magnetic memory device in Example 1;

FIGS. 8A and 8B are schematic partly sectional views of the interlayerinsulation layer and the like, for illustrating the method ofmanufacturing the nonvolatile magnetic memory device in Example 1,following FIG. 7C;

FIG. 9 is a schematic plan view of the recording layer in thenonvolatile magnetic memory device in Example 2 as the nonvolatilemagnetic memory device according to the fifth embodiment of the presentinvention;

FIG. 10 is a schematic plan view of the recording layer in thenonvolatile magnetic memory device in Example 2 as the nonvolatilemagnetic memory device according to the sixth embodiment of the presentinvention;

FIG. 11 is a schematic plan view of the recording layer in thenonvolatile magnetic memory device in Example 2 as the nonvolatilemagnetic memory device according to the seventh embodiment of thepresent invention;

FIG. 12 is a schematic plan view of the recording layer in thenonvolatile magnetic memory device in Example 2 as the nonvolatilemagnetic memory device according to the eight embodiment of the presentinvention;

FIGS. 13A and 13B show a pattern provided in a photomask in Example 3,and the plan-view shape of the recording layer obtained based on thepattern;

FIGS. 14A and 14B show a pattern provided in a photomask in Example 4,and the plan-view shape of the recording layer obtained based on thepattern;

FIG. 15 is a schematic partly sectional view of a magnetoresistancedevice applying inversion of magnetization by spin implantation;

FIG. 16 is a schematic plan view of a modified example of the recordinglayer in the nonvolatile magnetic memory device in Example 1;

FIG. 17 is a schematic plan view of another modified example of therecording layer in the nonvolatile magnetic memory device in Example 1;

FIGS. 18A to 18E show patterns obtained upon optical proximitycorrections;

FIG. 19 is a diagram showing an example of the distribution ofresistance of the recording layer constituting a TMR type nonvolatilemagnetic memory device;

FIG. 20 is a diagram schematically showing an asteroid curve in the TMRtype nonvolatile magnetic memory device;

FIG. 21 is a diagram schematically showing the dispersion of switchingmagnetic field (H_(Switch)) of the asteroid curve in the TMR typenonvolatile magnetic memory device; and

FIGS. 22A to 22F schematically show the plan-view shapes of tunnelmagnetoresistance devices in TMR type nonvolatile magnetic memorydevices according to the related art.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now, the present invention will be described below based on Examples,referring to the drawings.

EXAMPLE 1

Example 1 pertains to a nonvolatile magnetic memory device according tothe first to fourth embodiments of the present invention. Thenonvolatile magnetic memory device in Example 1 including amagnetoresistance device having a recording layer being formed of aferromagnetic material for storing information by use of variation inresistance depending on the magnetization inversion state thereof, andis specifically a nonvolatile magnetic memory device including a tunnelmagnetoresistance device using the TMR effect.

Here, in the nonvolatile magnetic memory device in Example 1 as thenonvolatile magnetic memory device according to the first embodiment ofthe present invention, as a schematic plan view of a recording layer 35is shown in FIG. 1, the plan-view shape (indicated by solid lines) ofthe recording layer 35 has a pseudo rhombic shape having four sidesSR_(m) (where “m” is any of 1, 2, 3, and 4). The sides SR_(m) indicatethe portions of the plan-view shape of the recording layer 35 which arelocated between the intersections BC, AD of the plan-view shape of therecording layer 35 with the longer axis LX (length: 2L_(L)) of thepseudo rhombic shape and the intersections AB, CD of the plan-view shapeof the recording layer 35 with the shorter axis SX (length: 2L_(S)) ofthe pseudo-rhombic shape. At least two of the four sides constitutingthe pseudo-rhombic shape (in Example 1, all the four sides SR_(m)) eachhave a smooth curve having a central portion CT thereof curved towardthe center of the pseudo-rhombic shape. The easy axis of magnetization(EA) of the recording layer 35 is substantially parallel to the longeraxis LX (indicated by dot-dash line) of the pseudo-rhombic shape, andthe hard axis of magnetization (HA) of the recording layer 35 issubstantially parallel to the shorter axis SX (indicated by dot-dashline) of the pseudo-rhombic shape. Further, the sides SR_(m)constituting the plan-view shape of the recording layer 35 are smoothlyconnected to each other.

Incidentally, at least two points of inflection are present in each ofthe sides SR_(m) each of which has the smooth curve having a centralportion CT thereof curved. Specifically, two inflection points (A₃, A₄)are present in the side SR₁, and two inflection points (B₃, B₄) arepresent in the side SR₂. Further, two inflection points (C₃, C₄) arepresent in the side SR₃, and two inflection points (D₃, D₄) are presentin the side SR₄. Incidentally, in the drawing, the points of inflectionare represented by solid circle.

Here, as shown in FIG. 1, the plan-view shape of the recording layer 35is substantially line symmetric with respect to the shorter axis SX ofthe pseudo-rhombic shape, and is substantially line symmetric withrespect also to the longer axis LX of the pseudo-rhombic shape.

Alternatively, in the nonvolatile magnetic memory device in Example 1 asthe nonvolatile magnetic memory device according to the secondembodiment of the present invention, as a schematic plan view of therecording layer 35 is shown in FIG. 2, the plan-view shape (indicated bysolid line) of the recording layer 35 include fourth sides SR_(m), andat least two of the four sides (in Example 1, all the four sides SR_(m))are each composed of a smooth curve. Besides, the plan-view shape of therecording layer 35 is inscribed in a virtual rhombus (indicated bytwo-dotted chain lines). In FIG. 2, the inscribing points arerepresented by mark “x”. Here, the virtual rhombus has a longer axis LXhaving a length (the distance from point AD to point BC) of 2L_(i-L),and a shorter axis SX orthogonally intersecting the longer axis LX atthe bisection point O of the longer axis LX and having a length (thedistance from point AB to point CD) of 2L_(i-s) [where L_(i-S)<L_(i-L)];the longer axis LX is substantially parallel to the easy axis (EA) ofthe recording layer 35, and the shorter axis SX is substantiallyparallel to the hard axis (HA) of the recording layer 35. Further, eachof the sides SR_(m) having smooth curves, contacts the correspondingside TL_(m) of the virtual rhombus at at least two points (just twopoints in Example 1). In FIG. 2, the points of contact are representedby mark “x”. In addition, the sides SR_(m) constituting the plan-viewshape of the recording layer 35 are smoothly connected to each other.

In the side SR₁ having a smooth curve for constituting the plan-viewshape of the recording layer 35,

-   -   (a) the point located closest to the shorter axis SX of the        virtual rhombus, of the at least two points of contact with the        side TL₁ of the virtual rhombus, is made to be the origin A₀        (0, 0) of a Gaussian coordinate system,    -   (b) the point located closest to the longer axis LX of the        virtual rhombus, of the at least two points of contact with the        side TL₁ of the virtual rhombus, is made to be A₁ (X₁, 0) [where        X₁>0],    -   (c) the intersection with the shorter axis SX of the virtual        rhombus is made to be AB₂ (X_(S), Y_(S)) [where X_(S)<0,        Y_(S)<0], and    -   (d) the intersection with the longer axis LX of the virtual        rhombus is made to be AD₅ (X_(L), Y_(L)) [where X_(L)>0,        Y_(L)<0].

Further, the side SR₁ is expressed by a real variable function F(X), andit is assumed that the intersection O between the longer axis LX and theshorter axis SX of the virtual rhombus is located in the third quadrantor the fourth quadrant (in the example shown, the fourth quadrant).

In this case, the real variable function F(X) has a continuousdifferential coefficient at each point in the interval X_(S)<X<X_(L),and the real variable function F(X) has two points of inflection (A₃,A₄) in the interval 0<X<X₁.

More specifically, in the interval X_(S)<X≦X_(A3) (X_(A3) is theX-coordinate of the inflection point A₃), the real variable functionF(X) is represented by a circle with a radius r_(S). Besides, in theinterval X_(A3)≦X≦X_(A4) (X_(A4) is the X-coordinate of the inflectionpoint A₄), the real variable function F(X) is represented by a circlewith a radius r_(SR). Further, in the interval X_(A4)<X≦X_(L), the realvariable function F(X) is represented by a circle with a radius r_(L).

In addition, in the side SR₂ composed of a smooth curve for constitutingthe plan-view shape of the recording layer 35,

-   -   (a) the point located closest to the shorter axis SX of the        virtual rhombus, of the at least two points of contact with the        side TL₂ of the virtual rhombus, is made to be the origin B₀        (0, 0) of a Gaussian coordinate system,    -   (b) the point located closest to the longer axis LX of the        virtual rhombus, of the at least two points of contact with the        side TL₂ of the virtual rhombus, is made to be B₁ (X₁, 0) [where        X₁>0],    -   (c) the intersection with the shorter axis SX of the virtual        rhombus is made to be AB₂ (X_(S), Y_(S)) [where X_(S)<0,        Y_(S)<0], and    -   (d) the intersection with the longer axis LX of the virtual        rhombus is made to be BC₅ (X_(L), Y_(L)) [where X_(L)>0,        Y_(L)<0].

Further, the side SR₂ is represented by a real variable function F(X),and it is assumed that the intersection O between the longer axis LX andthe shorter axis SX of the virtual rhombus is located in the thirdquadrant or the fourth quadrant (in the example shown, the fourthquadrant).

In this case, the real variable function F(X) has a continuousdifferential coefficient in each point in the interval X_(S)<X<X_(L),and the real variable function F(X) has two points of inflection (B₃,B₄) in the interval 0<X<X₁.

More specifically, in the interval X_(S)<X≦X_(B3) (X_(B3) is theX-coordinate of the inflection point B₃), the real variable functionF(X) is represented by a circle with a radius r_(S). Besides, in theinterval X_(B3)≦X≦X_(B4) (X_(B4) is the X-coordinate of the inflectionpoint B₄), the real variable function F(X) is represented by a circlewith a radius r_(SR). Further, in the interval X_(B4)<X≦X_(L), the realvariable function F(X) is represented by a circle with a radius r_(L).

Besides, in the side SR₃ composed of a smooth curve for constituting theplan-view shape of the recording layer 35,

-   -   (a) the point located closest to the shorter axis SX of the        virtual rhombus, of the at least two points of contact with the        side TL₃ of the virtual rhombus, is made to be the origin C₀        (0, 0) of a Gaussian coordinate system,    -   (b) the point located closest to the longer axis LX of the        virtual rhombus, of the at least two points of contact with the        side TL₃ of the virtual rhombus, is made to be C₁ (X₁, 0) [where        X₁>0],    -   (c) the intersection with the shorter axis SX of the virtual        rhombus is made to be CD₂ (X_(S), Y_(S)) [where X_(S)<0,        Y_(S)<0], and    -   (d) the intersection with the longer axis LX of the virtual        rhombus is made to be BC₅ (X_(L), Y_(L)) [where X_(L)>0,        Y_(L)<0].

Further, the side SR3 is expressed by a real variable function F(X), andit is assumed that the intersection O between the longer axis LX and theshorter axis SX of the virtual rhombus is located in the third quadrantor the fourth quadrant (in the example shown, the fourth quadrant).

In this case, the real variable function F(X) has a continuousdifferential coefficient at each point in the interval X_(S)<X<X_(L),and the real variable function F(X) has two points of inflection (C₃,C₄) in the interval 0<X<X₁.

More specifically, in the interval X_(S)<X≦X_(C3) (X_(C3) is theX-coordinate of the inflection point C₃), the real variable functionF(X) is represented by a circle with a radius r_(S). Besides, in theinterval X_(C3)≦X≦X_(C4) (X_(C4) is the X-coordinate of the inflectionpoint C₄), the real variable function F(X) is represented by a circlewith a radius r_(SR). Further, in the interval X_(C4)<X≦X_(L), the realvariable function F(X) is represented by a circle with a radius r_(L).

In addition, in the side SR₄ composed of a smooth curve for constitutingthe plan-view shape of the recording layer 35,

-   -   (a) the point located closest to the shorter axis SX of the        virtual rhombus, of the at least two points of contact with the        side TL₄ of the virtual rhombus, is made to be the origin D₀        (0, 0) of a Gaussian coordinate system,    -   (b) the point located closest to the longer axis LX of the        virtual rhombus, of the at least two points of contact with the        side TL₄ of the virtual rhombus, is made to be D₁ (X₁, 0) [where        X₁>0],    -   (c) the intersection with the shorter axis SX of the virtual        rhombus is made to be CD₂ (X_(S), Y_(S)) [where X_(S)<0,        Y_(S)<0], and    -   (d) the intersection with the longer axis LX of the virtual        rhombus is made to be AD₅ (X_(L), Y_(L)) [where X_(L)>0,        Y_(L)<0]

Further, the side SR₄ is expressed by a real variable function F(X), andit is assumed that the intersection O between the longer axis LX and theshorter axis SX of the virtual rhombus is located in the third quadrantor the fourth quadrant (in the example shown, the fourth quadrant).

In this case, the real variable function F(X) has a continuousdifferential coefficient at each point in the interval X_(S)<X<X_(L),and the real variable function F(X) has two points of inflection (D₃,D₄) in the interval 0<X<X₁.

More specifically, in the interval X_(S)<X≦X_(D3) (X_(D3) is theX-coordinate of the inflection point D₃), the real variable functionF(X) is represented by a circle with a radius r_(S). Besides, in theinterval X_(D3)≦X≦X_(D4) (X_(D4) is the X-coordinate of the inflectionpoint D₄), the real variable function F(X) is represented by a circlewith a radius r_(SR). Further, in the interval X_(D4)<X≦X_(L), the realvariable function F(X) is represented by a circle with a radius r_(L).

Incidentally, in the interval X_(S)<X<0, the first-order differentialcoefficient of the real variable function F(X) is a positive value; atX=0, the first-order differential coefficient of the real variablefunction F(X) is 0; and in the interval 0<X<X₁, the first-orderdifferential coefficient of the real variable function F(X) varies froma negative value to 0, and further to a positive value. At X=X₁, thefirst-order differential coefficient of the real variable function F(X)is 0; and in the interval X₁<X<X_(L), the first-order differentialcoefficient of the real variable function F(X) is a negative value.

Furthermore, in the interval X_(S)<X<X_(A3) (or X_(B3), X_(C3), X_(D3)),the second-order differential coefficient of the real variable functionF(X) is a negative value; at X=X_(A3) (or X_(B3), X_(C3), X_(D3)), thesecond-order differential coefficient of the real variable function F(X)is 0; in the interval X_(A3) (or X_(B3), X_(C3), X_(D3))<X<X_(A4) (orX_(B4), X_(C4), X_(D4)), the second-order differential coefficient ofthe real variable function F(X) is positive; and in the intervalX=X_(A4) (or X_(B4), X_(C4), X_(D4)), the second-order differentialcoefficient of the real variable function F(X) is a negative value.

In addition, assuming a Gaussian coordinate system with the longer axisLX of the virtual rhombus being the x-axis and with the shorter axis SXof the virtual rhombus being the y-axis, when the side SR₁ and the sideSR₂ are collectively expressed by a real variable function F(x) and theside SR₃ and the side SR₄ are collectively expressed by the realvariable function F(x), the real variable function F(x) has a continuousdifferential coefficient at each point in the interval a<x<b (where a isthe minimum allowable value of x in the real variable function F(x), andb is the maximum allowable value of x in the real variable functionF(x)). Besides, the first-order differential coefficient of the realvariable function F(x) at x=0 is 0, and the first-order differentialcoefficient of the real variable function F(x) at y=0 is ∞.

In the recording layer 35 shown in FIG. 2, also, the plan-view shape issubstantially line symmetric with respect to the shorter axis SX of thevirtual rhombus, and is substantially line symmetric with respect alsoto the longer axis LX of the virtual rhombus.

Alternatively, in the nonvolatile magnetic memory device in Example 1 asthe nonvolatile magnetic memory device according to the third embodimentof the present invention, as the schematic plan view of the recordinglayer 35 is shown in FIG. 3, the plan-view shape of the recording layer35 includes a first shape 35A (indicated by solid line in FIG. 3), andtwo projected portions 35B, 35C (indicated by solid lines in FIG. 3)projected from the first shape 35A. The two projected portions 35B, 35Care located on the projected portion axis (indicated by dot-dash line inFIG. 3). Here, the projected portion axis passes through the center O ofthe first shape 35A, and orthogonally intersects the first shape axis(indicated by dot-dash line in FIG. 3) passing through the center O ofthe first shape 35A. In addition, the easy axis (EA) of the recordinglayer 35 is substantially parallel to the first shape axis, and the hardaxis (HA) of the recording layer 35 is substantially parallel to theprojected portion axis. Further, let the length of the first shape 35Aalong the first shape axis be 2L_(L), and let the distance between tipend portions of the two projected portions 35B and 35C along theprojected portion axis be 2L_(S), then the relationship L_(L)>L_(S) issatisfied. In addition, each of the portions where the visible outlineof the first shape 35A intersects the visible outlines of the projectedportions 35B, 35C has a smooth curve (indicated by broken line in FIG.3) curved toward the center O of the first shape 35A.

The first shape 35A is a flat oval, i.e., a figure composed of acombination of two semi-circles (radius: r_(L)) with two line segments.In addition, the projected portions 35B and 35C are each a figurecomposed of a part of a circle (radius: r_(S)).

Incidentally, the plan-view shape of the recording layer 35 issubstantially line symmetric with respect to the projected portion axis,and is substantially line symmetric with respect to the first shapeaxis.

Alternatively, in the nonvolatile magnetic memory device in Example 1 asthe nonvolatile magnetic memory device according to the fourthembodiment of the present invention, as the schematic plan view of therecording layer 35 is shown in FIG. 4, the plan-view shape of therecording layer 35 has a superposed shape in which a first shape 35D anda second shape 35E having a center O coinciding with the center O of thefirst shape 35D are superposed on each other so that the second shape35E is projected from the first shape 35D at two positions. The firstshape axis passing through the center O of the first shape 35D and thesecond shape axis passing through the center O of the second shape 35Eorthogonally intersect each other. Further, the easy axis (EA) of therecording layer 35 is substantially parallel to the first shape axis,and the hard axis (HA) of the recording layer 35 is substantiallyparallel to the second shape axis. Besides, let the length of the firstshape 35D along the first shape axis be 2L_(L), and let the length ofthe second shape 35E along the second shape axis be 2L_(S), then therelationship L_(L)>L_(S) is satisfied. Further, each of the portionswhere the visible outline of the first shape 35D and the visible outlineof the second shape 35E intersect is composed of a smooth curve(indicated by broken line in FIG. 4) curved toward the center O of thefirst shape 35D.

The first shape 35D is a flat oval, i.e., a figure composed of acombination of two semi-circles (radius: r_(L)) with two line segments.In addition, the second shape 35E is also a flat oval, i.e., a figurecomposed of a combination of two semi-circles (radius: r_(S)) with twoline segments.

Incidentally, the recording layer 35 is substantially line symmetricwith respect to the second shape axis, and is substantially linesymmetric with respect to the first shape axis.

As a schematic partly sectional view is shown in FIG. 6, one tunnelmagnetoresistance device TMJ in Example 1 has a laminate structure inwhich a first ferromagnetic material layer 31, a tunnel insulation film34 formed of AlO_(x), and a second ferromagnetic material layer 35 (alsocalled free layer or recording layer) formed of a Ni—Fe alloy areprovided in this order from the lower side. The first ferromagneticmaterial layer 31 has a laminate structure of an antiferromagneticmaterial layer 32 and a magnetization fixation layer 33. Themagnetization fixation layer 33 may have a multilayer structure (e.g.,ferromagnetic material layer/metal layer/ferromagnetic material layer)having the synthetic antiferromagnet (SAF) coupling, and, morespecifically, has a three-layer structure in which a Co—Fe layer, a Rulayer, and a Co—Fe layer are provided in this order from the lower side.The magnetization fixation layer 33 undergoes exchange coupling with theantiferromagnetic material layer 32, whereby pinning of themagnetization direction is effected. The magnetization direction of thesecond ferromagnetic material layer (recording layer) 35 is changed tobe parallel to or anti-parallel to the magnetization fixation layer 33,by a magnetic field applied externally. The first ferromagnetic materiallayer 31 is electrically insulated from a write word line RWL through alower interlayer insulation layer 24. Here, the write word line RWLextends in a first direction (the direction perpendicular to the papersurface of the drawing). On the other hand, the second ferromagneticmaterial layer 35 is electrically connected to a bit line BL, through atop coat film 36 formed of copper (Cu), tantalum (Ta), titanium (Ti),tungsten (W), TiN, TaN, WN, or the like. The top coat film 36 is incharge of prevention of mutual diffusion of the atoms constituting thebit line BL and the atoms constituting the ferromagnetic material layer(recording layer) 35, reduction of the contact resistance, andprevention of the oxidation of the ferromagnetic material layer(recording layer) 35. An upper interlayer insulation layer 26 covers thetunnel magnetoresistance device TMJ and the lower interlayer insulationlayer 24. The bit line BL is formed on the upper interlayer insulationlayer 26, and extends in a second direction (the left-right direction inthe drawing) which is different from (specifically, orthogonal to) thefirst direction. In FIG. 6, reference numeral 37 denotes an extractionelectrode connected to the lower surface of the antiferromagneticmaterial layer 32.

A selection transistor TR composed of a MOSFET is formed on asemiconductor substrate 10. More specifically, the selection transistorTR is formed in an active region surrounded by device isolation regions11, and includes a gate electrode 12, a gate insulation film 13, andsource/drain regions 14A, 14B. An interlayer insulation layer 21 formedof SiO₂, for example, covers the selection transistor TR. A contact hole22 formed of a tungsten plug is formed in an opening portion provided inthe interlayer insulation layer 21, and is connected to the source/drainregion 14B on one side of the selection transistor TR. The contact hole22 is connected further to a landing pad portion 23 formed on theinterlayer insulation layer 22. A write word line RWL formed of an Al—Cualloy is also formed on the interlayer insulation layer 21. The lowerinterlayer insulation layer 24 is formed on the write word line RWL andthe interlayer insulation layer 21. The extraction electrode 37 isformed on the lower interlayer insulation layer 24, and the extractionelectrode 37 is connected to the landing pad portion 23, through thecontact hole 25 formed of the tungsten plug provided in the lowerinterlayer insulation layer 24. Incidentally, the source/drain region14A on the other side of the selection transistor TR is connected to asense line 16 through a contact hole 15.

In some cases, the selection transistor TR may be unnecessary.

Now, a method of manufacturing an MRAM in Embodiment 1 will be describedbelow, referring to FIGS. 7A to 7C and FIGS. 8A and 8B, which areschematic partly sectional views of the lower interlayer insulationlayer 24 and the like. Incidentally, in FIGS. 7A to 7C and FIGS. 8A and8B, the selection transistor TR and the like are omitted.

[Step 100]

First, a MOSFET functioning as the selection transistor TR is formed ona semiconductor substrate 10 composed of a silicon semiconductorsubstrate. For this purpose, device separation regions 11 having atrench structure, for example, are formed based on the known method.Incidentally, the device separation regions may have a LOCOS structureor may have a combination of the LOCOS structure and the trenchstructure. Thereafter, the surface of the semiconductor substrate 10 isoxidized, for example, by the pyrogenic process, to form a gateinsulation film 13. Next, a polysilicon layer doped with an impurity isformed on the entire surface by a CVD process, and the polysilicon layeris patterned, to form a gate electrode 12. Incidentally, the gateelectrode 12 may not necessarily be composed of a polysilicon layer, andmay be composed of a polycide or metal silicide. Next, ions areimplanted into the semiconductor substrate 10, to form an LDD structure(not shown). Thereafter, an SiO₂ layer is formed on the entire surfaceby a CVD process, and the SiO₂ layer is etched back, to form a gate sidewall (not shown) at the side surface of the gate electrode 12. Next,ions are implanted into the semiconductor substrate 10, followed by anactivation annealing treatment for the impurity thus ion-implanted, toform source/drain regions 14A and 14B.

Next, a lower layer of the interlayer insulation layer composed of SiO₂is formed on the whole surface by a CVD process, and the lower layer ofthe interlayer insulation layer is polished by a chemical mechanicalpolishing process (CMP process). Thereafter, an opening portion isformed in the lower layer of the interlayer insulation layer on theupper side of the source/drain region 14A on the basis of thelithography technology and the RIE process, and then a polysilicon layerdoped with an impurity is formed on the lower layer of the interlayerinsulation layer inclusive of the inside of the opening portion by a CVDprocess. Next, the polysilicon layer on the lower layer of theinterlayer insulation layer is patterned, whereby a sense line 16 can beformed on the lower layer of the interlayer insulation layer. The senseline 16 and the source/drain region 14A are connected to each otherthrough a contact hole 15 formed in the lower layer of the interlayerinsulation layer. Thereafter, an upper layer of the interlayerinsulation layer which is composed of BPSG is formed on the entiresurface by a CVD process. Incidentally, it is preferable that, after theformation of the upper layer of the interlayer insulation layer composedof the BPSG, a heat treatment in a nitrogen atmosphere under theconditions of 900° C.×20 min, for example, is conducted for reflowing ofthe upper layer of the interlayer insulation layer. Further, ifnecessary, it is preferable that the top surface of the upper layer ofthe interlayer insulation layer is chemically and mechanically polishedby the CMP process, for example, to planarize the upper layer of theinterlayer insulation layer, or the resist etch-back process is carriedout to planarize the upper layer of the interlayer insulation layer.Incidentally, the lower layer of the interlayer insulation layer and theupper layer of the interlayer insulation layer will hereinafter bereferred to simply as the interlayer insulation layer 21.

[Step 120]

Thereafter, an opening portion is formed in the interlayer insulationlayer 21 on the upper side of the source/drain region 14B by an RIEprocess, and then a contact hole 22 connected to the source/drain region14B of the selection transistor TR is formed in the opening portion. Thetop surface of the contact hole 22 is substantially flush with thesurface of the interlayer insulation layer 21. The opening portion isfilled with tungsten by a blanket tungsten CVD process, whereby thecontact hole 22 can be formed. Incidentally, it is preferable that,before filling the opening portion with tungsten, a Ti layer and a TiNlayer are sequentially formed on the interlayer insulation layer 21inclusive of the inside of the opening portion by a magnetron sputteringprocess, for example. Here, the Ti layer and the TiN layer are formedfor the purposes of obtaining an ohmic low contact resistance,preventing damages from being generated in the semiconductor substrate10 during the blanket tungsten CVD process, and enhancing the adhesionof tungsten. In the drawings, the Ti layer and the TiN layer areomitted. The tungsten layer, the TiN layer and the Ti layer on theinterlayer insulation layer 21 may be removed by the chemical mechanicalpolishing process (CMP process). Besides, polysilicon doped with animpurity may be used, in place of tungsten. Thereafter, a write wordline RWL and a landing pad portion 23 are formed on the interlayerinsulation layer 21 by a known method.

[Step 130]

Thereafter, a lower interlayer insulation layer 24 is formed on theentire surface. Specifically, the lower interlayer insulation layer 24formed of SiO₂ is formed on the interlayer insulation layer 21 inclusiveof the write word line RWL and the landing pad portion 23, based on anHDP (High Density Plasma) CVD process, and then the lower interlayerinsulation layer 24 is subjected to a planarizing treatment. Thereafter,an opening portion is provided in the portion of the lower interlayerinsulation layer 24 on the upper side of the landing pad portion 23, andthe opening portion is filled with tungsten by the blanket tungsten CVDprocess, whereby a contact hole 25 can be formed.

[Step 140]

Next, for forming an extraction electrode 37 on the lower interlayerinsulation layer 24, a Ta layer 37A having a thickness of 10 nm isformed by a sputtering process. Exemplary conditions for formation ofthe Ta layer 37A are given in Table 1 below.

[Step 150]

Thereafter, a first ferromagnetic material layer 31 (anantiferromagnetic material layer 32 formed of a Pt—Mn alloy with athickness of 20 nm, and a magnetization fixation layer 33 having athree-layer structure of a Co—Fe layer, a Ru layer, and a Co—Fe layer inthis order from the lower side, and having SAF), a tunnel insulationfilm 34 formed of AlO_(x), a recording layer (second ferromagneticmaterial layer) 35, and a top coat film 36 are sequentially formed onthe entire surface. Exemplary conditions for formation of these layersare given in Tables 2 to 6 below. In this manner, the structure shown inFIG. 7A can be obtained. TABLE 1 Conditions for Formation of 10 nm-thickTa Layer Process gas: argon = 100 sccm Atmospheric pressure: 0.6 Pa DCpower: 200 W

TABLE 2 Conditions for Formation of 20 nm-thick Pt—Mn AlloyAntiferromagnetic Material Layer 32 Process gas: argon = 100 sccmAtmospheric pressure: 0.6 Pa DC power: 200 W

TABLE 3 Conditions for Formation of Magnetization Fixation Layer 33Lowermost layer: 2 nm-thick Co—Fe alloy layer Process gas: argon = 50sccm Atmospheric pressure: 0.3 Pa DC power: 100 W Intermediate layer: 1nm-thick Ru layer Process gas: argon = 50 sccm Atmospheric pressure: 0.3Pa DC power: 50 W Uppermost layer: 2 nm-thick Co—Fe alloy layer Processgas: argon = 50 sccm Atmospheric pressure: 0.3 Pa DC power: 100 W

TABLE 4 Conditions for Formation of AlO_(x) Tunnel Insulation FilmFormation of 1 to 2 nm-thick Al film Process gas: argon = 50 sccmAtmospheric pressure: 0.3 Pa DC power: 50 W Oxidation of Al film Gasused: oxygen = 10 sccm Atmospheric pressure: 0.3 Pa

TABLE 5 Conditions for Formation of 5 nm-thick Co—Fe Alloy RecordingLayer 35 Process gas: argon = 50 sccm Atmospheric pressure: 0.3 Pa DCpower: 200 W

TABLE 6 Conditions for Formation of 100 nm-thick TiN Top coat film 36Process gas: argon = 65 sccm Atmospheric pressure: 0.3 Pa DC power: 10kW

[Step 160]

Thereafter, a hard mask layer for etching is formed on the top coat film36. The hard mask layer has a two-layer structure including an SiN layer40 and an SiO₂ layer 41 in this order from the lower side. Examples ofother materials for constituting the hard mask layer include SiC andSiON. The hard mask layer may be of a single-layer configuration. Insome cases, the hard mask layer is formed to also have the functions ofpreventing reflection in the lithography step, stopping etching,preventing diffusion of metal, and so on. Here, as an example, a 50nm-thick SiN layer 40 is formed by use of a parallel flat plate electricpower plasma CVD apparatus, and the SiO₂ layer 41 is formed by use of abias high-density plasma CVD (HDP-CVD) apparatus. Exemplary conditionsfor formation of these layers are given in Tables 7 and 8 below. TABLE 7Conditions for Formation of SiN Layer Process gas: monosilane/ammonia/N₂= 260 sccm/100 sccm/4000 sccm Pressure: 565 Pa

TABLE 8 Conditions for Formation of SiO₂ Layer Process gas:monosilane/O₂/argon = 60 sccm/120 sccm/130 sccm RF power Top: 1.5 kWSide: 3 kW

[Step 170]

Next, a resist material is applied to the whole surface, and then aresist film 42 to be a mask for forming a tunnel magnetoresistancedevice is formed on the hard mask layer by a lithography technique. Inthis manner, the structure shown in FIG. 7B can be obtained.

[Step 180]

Then, the SiO₂ layer 41 constituting the hard mask layer is patterned bya reactive ion etching process using the resist film 42 as a mask.Exemplary etching conditions in this case are given in Table 9 below.Thereafter, the resist film 42 is removed by an oxygen plasma ashingtreatment and an organic cleaning after-treatment. Next, the SiN layer40 constituting the hard mask layer is etched by a reactive ion etchingprocess using the SiO₂ layer 41 as a mask. Exemplary etching conditionsin this case are given in Table 10 below. In this manner, the structureshown in FIG. 7C can be obtained. TABLE 9 Etching Conditions for SiO₂Layer Gas used: C₄F₈/CO/Ar/O₂ = 10 sccm/50 sccm/200 sccm/4 sccm RFpower: 1 kW Pressure: 5 Pa Temperature: 20° C.

TABLE 10 Etching Conditions for SiN Layer Gas used: CHF₃/Ar/O₂ = 20sccm/200 sccm/20 sccm RF power: 1 kW Pressure: 6 Pa Temperature: 20° C.

[Step 190]

Next, using the hard mask layer 41, 40 as a mask, the top coat film 36and the recording layer 35 are patterned by a reactive ion etchingprocess (see FIGS. 8A and 8B). Exemplary etching conditions in this caseare given in Tables 11 and 12 below. TABLE 11 Etching Conditions for TopCoat Film 36 Gas used: Cl₂/BCl₃/N₂ = 60 sccm/80 sccm/10 sccm Sourcepower:  1 kW Bias power: 150 W Pressure:  1 Pa

TABLE 12 Etching Conditions for Recording Layer 35 Gas used: Cl₂/O₂/Ar =50 sccm/20 sccm/20 sccm Source power:  1 kW Bias power: 150 W Pressure: 1 Pa

Here, in the etching step for the recording layer 35, a time setting ismade so that the etching is stopped during the etching of the tunnelinsulation film 34. Incidentally, the etching conditions are so set asto obviate the problem that the etching products would deposit on theside walls of the recording layer 35 and the tunnel insulation film 34with the result of an electrical shortcircuit between the recordinglayer 35 and the magnetization fixation layer 33, even in the case wherethe tunnel insulation film 34 is etched during the etching step for therecording layer 35 and, further, the etching proceeds to a part of themagnetization fixation layer 33. Thereafter, an ashing treatment and awater washing or organic washing treatment are carried out.

The top coat film 36 and the recording layer 35 may be patterned basedon an ion milling process (ion beam etching process), instead of beingpatterned by the reactive ion etching process. Incidentally, after theetching, the deposits on the side walls, the etching gas residue,particles, etching residues and the like are removed by washing withwater or an organic cleaning liquid, aerosol or the like

Thereafter, the magnetization fixation layer 33 and theantiferromagnetic material layer 32 are patterned, and further the Talayer 37A is patterned by a known method, whereby the extractionelectrode 37 can be obtained. In this manner, it is possible to obtain anonvolatile magnetic memory device including the tunnelmagnetoresistance device TMJ having the recording layer 35 formed of aferromagnetic material for storing information by use of variation inresistance depending on the magnetization inversion state thereof.

In the nonvolatile magnetic memory device including the tunnelmagnetoresistance device using the TMR effect in Example 1, let thelength of the longer axis LX of the pseudo-rhombic shape shown in FIG. 1be 2L_(L), and let the length of the shorter axis SX of thepseudo-rhombic shape be 2L_(S), then the relationship 2L_(L)/2L_(S)=1190nm/560 nm=2.13 was adopted, as shown in FIG. 3 or 4. In addition, letthe radius of curvature of the plan-view shape of the recording layer 35at the intersections BC and AD between the longer axis LX of thepseudo-rhombic shape and the plan-view shape of the recording layer 35(or the radius of curvature of the plan-view shape of the recordinglayer 35 at the intersections BC and AD between the shorter axis SX ofthe pseudo-rhombic shape and the plan-view shape of the recording layer35) be r_(L), let the radius of curvature of the plan-view shape of therecording layer 35 at the intersections AB and CD between the shorteraxis SX of the pseudo-rhombic shape and the plan-view shape of therecording layer 35 (or the radius of curvature of the plan-view shape ofthe recording layer 35 at the intersections AD and CD between theprojected portion axis or the second shape axis and the plan-view shapeof the recording layer 35) be r_(S), then the relationshipsr_(L)/L_(S)=145 nm/280 nm=0.52 and r_(S)/L_(L)=480 nm/595 nm=0.81 wereadopted. Or, as shown in FIG. 2, the relationship 2L_(i-L)/2L_(i-S)=1810nm/640 nm=2.83 was adopted. In addition, let the radius of curvature ofthe plan-view shape of the recording layer 35 at the intersections BC₅and AD₅ between the longer axis LX of the virtual rhombus and theplan-view shape of the recording layer 35 be r_(L), and let the radiusof curvature of the plan-view shape of the recording layer 35 at theintersections AB₂ and CD₂ between the shorter axis SX of the virtualrhombus and the plan-view shape of the recording layer 35 be r_(S), thenthe relationships r_(L)/L_(i-S)=145 nm/320 nm=0.45 and r_(S)/L_(i-L)=480nm/905 nm=0.53 were adopted. Furthermore, in the interval 0<X<X₁ in theside composed of a smooth curve, let the maximum distance between theside SR_(m) composed of the smooth curve and the corresponding side TLmof the virtual rhombus be D_(MAX), then the relationship D_(MAX)/X₁=18nm/360 nm=1/20 was adopted. The above-mentioned values are collectivelygiven in Table 13 below. TABLE 13 L_(L) = 595 nm L_(S) = 280 nm L_(i-L)= 905 nm L_(i-S) = 320 nm r_(L) = 145 nm r_(S) = 480 nm D_(MAX) = 18 nmX₁ = 360 nm

In the nonvolatile magnetic memory device including the tunnelmagnetoresistance device having the above-mentioned data, a test of oncemeasuring the magnetic field H_(C) at the time of inversion of themagnetization direction of the recording layer 35 as a minor loopwaveform, determining the average H_(AVE) and the standard deviation σof the magnetic field H_(C), and further determining σ/H_(AVE) (SOA),was performed for 50 to 100 specimens. Examples of the minor loopwaveform and an electron microphotograph of the plan-view shape of therecording layer 35 are shown in FIG. 5.

On the other hand, for comparison, a nonvolatile magnetic memory deviceincluding a tunnel magnetoresistance device in which the plan-view shapeof the recording layer 35 has a rectangle with the length in the easyaxis direction of 1160 nm and with the length in the hard axis directionof 540 nm was manufactured in the same semiconductor substrate (in thesame wafer) as that for the nonvolatile magnetic memory device ofExample 1, then the average H_(AVE) and the standard deviation σ of themagnetic field H_(C) were determined similarly to the above, and furtherσ/H_(AVE) (SOA) was determined. Incidentally, this test will be referredto as Comparative Example 1.

Furthermore, for comparison, a nonvolatile magnetic memory deviceincluding a tunnel magnetoresistance device in which the plan-view shapeof the recording layer 35 has an ellipse with the length of the longeraxis in the easy axis direction of 1160 nm and with the length of theshorter axis in the hard axis direction of 540 nm was manufactured inthe same semiconductor substrate (in the same wafer) as that for thenonvolatile magnetic memory devices of Example 1 and Comparative Example1, then the average H_(AVE) and the standard deviation σ of the magneticfield H_(C) were determined similarly to the above, and furtherσ/H_(AVE) (SOA) was determined. Incidentally, this test will be referredto as Comparative Example 2.

The results of Example 1, Comparative Example 1, and Comparative Example2 are shown in Table 15.

EXAMPLE 2

Example 2 pertains to the nonvolatile magnetic memory devices accordingto the fifth to eighth embodiments of the present invention. Thenonvolatile magnetic memory deice of Example 2 including amagnetoresistance device having a recording layer formed of aferromagnetic material for storing information by variation inresistance depending on the magnetization inversion state thereof isalso a nonvolatile magnetic memory device including a tunnelmagnetoresistance device using the TMR effect, in the same manner as inExample 1. Incidentally, the tunnel magnetoresistance device TMJ and thenonvolatile magnetic memory device in Example 2 also have the sameconfigurations and structures as those of the tunnel magnetoresistancedevice TMJ and the nonvolatile magnetic memory device in Example 1,except for the difference in the plan-view shape of the recording layer;therefore, the following description will be made only of the plan-viewshape of the recording layer.

Here, in the nonvolatile magnetic memory device of Example 2 as thenonvolatile magnetic memory device according to the fifth embodiment ofthe present invention, as a schematic plan view of a recording layer 135is shown in FIG. 9, the plan-view shape (indicated by solid line) of therecording layer 135 has a pseudo isosceles triangular shape having threesides SR_(n) (where “n” is any of 1, 2, and 3). The oblique lines SR₁and SR₂ of the pseudo isosceles triangular shape are each composed of asmooth curve having a central portion CT thereof curved toward thecenter of the pseudo isosceles triangular shape. The easy axis (EA) ofthe recording layer 135 is substantially parallel to the base SR₃ of thepseudo isosceles triangular shape, and the hard axis (HA) of therecording layer 135 is substantially orthogonal to the base SR₃ of thepseudo isosceles triangular shape. Further, the sides SR_(n)constituting the plan-view shape of the recording layer 135 are smoothlyconnected to each other.

At least two points of inflection are present in each of the obliquelines of the pseudo isosceles triangular shape. Specifically, twoinflection points (A₃, A₄) are present in the oblique line SR₁, and twoinflection points (B₃, B₄) are present in the oblique line SR₂.

Here, as shown in FIG. 9, the plan-view shape of the recording layer 135is substantially line symmetric with respect to the perpendicularbisector of the base of the pseudo isosceles triangular shape.

The length of the imaginary base IB of the pseudo isosceles triangularshape shown in FIG. 9 is 2L_(B), the virtual height is H, the averageradius of curvature of the plan-view shape of the recording layer 135 atthe portions where the oblique lines SR₁ and SR₂ of the pseudo isoscelestriangular shape are smoothly connected to the base SR₃ is r_(L), andthe radius of curvature of the plan-view shape of the recording layer135 at the intersection AB of the two oblique lines SR₁ and SR₂ of thepseudo isosceles triangular shape is r_(S). Here, the intersection ofthe two oblique lines SR₁ and SR₂ of the pseudo isosceles triangularshape means the intersection AB at which the perpendicular bisector IHof the imaginary base IB intersects a curve obtained by connecting thetwo oblique lines SR₁ and SR₂ of the pseudo isosceles triangular shapeinto one line. In addition, the imaginary base IB of the pseudoisosceles triangular shape means an imaginary line which, when the baseSR₃ of the pseudo isosceles triangular shape is approximated by astraight line (base approximation straight line), is parallel to thebase approximation straight line and passes through a point located onthe side of the intersection of the two oblique lines SR₁ and SR₂ of thepseudo isosceles triangular shape and spaced from the base approximationstraight line by a distance r_(L). Further, the length 2L_(B) of theimaginary base is defined as the distance between the intersectionsbetween the plan-view shape of the recording layer 135 and the imaginarybase IB at the portions where the oblique lines SR₁ and SR₂ of thepseudo isosceles triangular shape are smoothly connected to the base SR₃(the distance between point BC and point AC). In addition, the virtualheight H is defined as the distance from the intersection AB of the twooblique lines SR₁ and SR₂ of the pseudo isosceles triangular shape tothe imaginary base IB. The length 2L_(B) of the imaginary base IB andthe virtual height H satisfy the relationship of H<L_(B).

Alternatively, in the nonvolatile magnetic memory device of Example 2 asthe nonvolatile magnetic memory device according to the sixth embodimentof the present invention, as a schematic plan view of a recording layer135 is shown in FIG. 10, the plan-view shape (indicated by solid line)of the recording layer 135 has three sides SR_(n), and at least two ofthe three sides (in Example 2, the sides SR₁ and SR₂) are each composedof a smooth curve. Besides, the plan-view shape of the recording layer135 is inscribed in a virtual isosceles triangle (indicated bytwo-dotted chain line). Incidentally, in FIG. 10, the inscribing pointsare indicated by mark “x”. Here, the virtual isosceles triangle has animaginary base IB (indicated by dot-dash line) having a length 2L_(i-B),and the imaginary height (the distance from point O to point AB) isH_(i) [where H_(i)<L_(i-B)]. Incidentally, the imaginary base IB of thevirtual isosceles triangle means an imaginary line which is parallel tothe base TL₃ of the virtual isosceles triangle and passes through apoint located on the side of the intersection of the two oblique linesTL₁ and TL₂ of the virtual isosceles triangle and spaced from the baseTL₃ of the virtual isosceles triangle by a distance r_(L), where r_(L)is the average radius of curvature of the plan-view shape of therecording layer 135 at the portions where the side SR₃ constituting theplan-view shape 135 and corresponding to the base TL₃ of the virtualisosceles triangle is smoothly connected to the sides SR₁ and SR₂constituting the plan-view shape of the recording layer 135 andcorresponding to the oblique lines TL₁ and TL₂ of the virtual isoscelestriangle. In addition, the length 2L_(i-B) of the imaginary base IB isthe distance between the intersections BC and AC at which the imaginarybase IB intersects the two oblique lines TL₁ and TL₂ of the virtualisosceles triangle. Further, the imaginary height H_(i) is the distancefrom the intersection AB of the two oblique lines TL₁ and TL₂ of thevirtual isosceles triangle to the imaginary base IB. Besides, the baseSR₃ is substantially parallel to the easy axis (EA) of the recordinglayer 135, and the perpendicular to the base SR₃ is substantiallyparallel to the hard axis (HA) of the recording layer 135. Furthermore,each of the sides SR₁ and SR₂ composed of smooth curves contacts thecorresponding side TL₁ or TL₂ at at least two points (in Example 2, twopoints). Incidentally, in FIG. 10, the point of contact is indicated bymark “x”. Moreover, the sides SR_(n) constituting the plan-view shape ofthe recording layer 135 are smoothly connected to each other.

In the oblique line SR₁ including a smooth curve and constituting theplan-view shape of the recording layer 135,

-   -   (a) the point closest to the intersection AB between the two        oblique lines TL₁ and TL₂ of the virtual isosceles triangle, of        at least two points of contact with the oblique line TL₁, is        made to be the origin A₀ (0, 0) of a Gaussian coordinate system,    -   (b) the point closest to the intersection AC between the oblique        line TL₁ and the base TL₃ of the virtual isosceles triangle, of        at least two points of contact with the oblique line TL₁, is        made to be A₁ (X₁, 0) [where X₁>0],    -   (c) the intersection with the perpendicular bisector of the base        TL₃ of the virtual isosceles triangle is made to be AB₂ (X_(S),        Y_(S)) [where X_(S)<0, Y_(S)<0], and    -   (d) the intersection with the imaginary base IB of the virtual        isosceles triangle is made to be A₅ (X_(L), Y_(L)) [where        X_(L)>0, Y_(L)<0].

Further, the oblique line SR₁ is represented by a real variable functionF(X), and it is assumed that the intersection between the perpendicularbisector of the base of the virtual isosceles triangle and the base islocated in the third quadrant or the fourth quadrant (in the exampleshown, the fourth quadrant).

In this case, the real variable function F(X) has a continuousdifferential coefficient at each point in the interval X_(S)<X<X_(L),and has two points of inflection (A₃, A₄) in the interval 0<X<X₁.

More specifically, in the interval X_(S)<X≦X_(A3) (X_(A3) is theX-coordinate of the inflection point A₃), the real variable functionF(X) is represented by a circle with a radius r_(S). Besides, in theinterval X_(A3)≦X≦X_(A4) (X_(A4) is the X-coordinate of the inflectionpoint A₄), the real variable function F(X) is represented by a circlewith a radius r_(SR). Further, in the interval X_(A4)<X≦X_(L), the realvariable function F(X) is represented by a circle with a radius r_(L).

In addition, in the oblique line SR₂ including a smooth curve andconstituting the plan-view shape of the recording layer 135,

-   -   (a) the point closest to the intersection AB between the two        oblique lines TL₁ and TL₂ of the virtual isosceles triangle, of        at least two points of contact with the oblique line TL₂, is        made to be the origin B₀ (0, 0) of a Gaussian coordinate system,    -   (b) the point closest to the intersection BC between the oblique        line TL₂ and the base TL₃ of the virtual isosceles triangle, of        at least two points of contact with the oblique line TL₂, is        made to be B₁ (X₁, 0) [where X₁>0],    -   (c) the intersection with the perpendicular bisector of the base        TL₃ of the virtual isosceles triangle is made to be AB₂ (X_(S),        Y_(S)) [where X_(S)<0, Y_(S)<0], and    -   (d) the intersection with the imaginary base IB of the virtual        isosceles triangle is made to be B₅ (X_(L), Y_(L)) [where        X_(L)>0, Y_(L)<0].

Further, the oblique line SR₂ is represented by a real variable functionF(X), and it is assumed that the intersection between the perpendicularbisector of the base of the virtual isosceles triangle and the base islocated in the third quadrant or the fourth quadrant (in the exampleshown, the fourth quadrant).

In this case, the real variable function F(X) has a continuousdifferential coefficient at each point in the interval X_(S)<X<X_(L),and has two points of inflection (B₃, B₄) in the interval 0<X<X₁.

More specifically, in the interval X_(S)<X≦X_(B3) (X_(B3) is theX-coordinate of the inflection point B₃), the real variable functionF(X) is represented by a circle with a radius r_(S). Besides, in theinterval X_(B3)≦X≦X_(B4) (X_(B4) is the X-coordinate of the inflectionpoint B₄), the real variable function F(X) is represented by a circlewith a radius r_(SR). Further, in the interval X_(B4)<X≦X_(L), the realvariable function F(X) is represented by a circle with a radius r_(L).

Incidentally, in the interval X_(S)<X<0, the first-order differentialcoefficient of the real variable function F(X) is a positive value; atX=0, the first-order differential coefficient of the real variablefunction F(X) is 0; and in the interval 0<X<X₁, the first-orderdifferential coefficient of the real variable function F(X) varies froma negative value to 0 and, further, to a positive value. In addition, atX=X₁, the first-order differential coefficient of the real variablefunction F(X) is 0, and, when X exceeds X₁, the first-order differentialcoefficient of the real variable function F(X) takes a negative value.

Further, in the interval X_(S)<X<X_(A3) (or X_(B3)), the second-orderdifferential coefficient of the real variable function F(X) is anegative value; at X=X_(A3) (or X_(B3)), the second-order differentialcoefficient of the real variable function F(X) is 0; in the intervalX_(A3) (or X_(B3))<X<X_(A4) (or X_(B4)), the second-order differentialcoefficient of the real variable function F(X) is positive; at X=X_(A4)(or X_(B4)), the second-order differential coefficient of the realvariable function F(X) is 0; and, in the interval X<X_(A4) (or X_(B4)),the second-order differential coefficient of the real variable functionF(X) is a negative value.

Besides, when a Gaussian coordinate system is assumed with the imaginarybase IB of the virtual isosceles triangle as the x-axis and with theperpendicular bisector of the imaginary base IB as the y-axis and whenthe oblique line SR₁ and the oblique line SR₂ are collectivelyrepresented by a real variable function F(x), then the real variablefunction F(x) has a continuous differential coefficient at each point inthe interval a<x<b (where a is the minimum allowable value of x in thereal variable function F(x), and b is the maximum allowable value of xin the real variable function F(x)). In addition, the first-orderdifferential coefficient of the real variable function F(x) at x=0 is 0,and the first-order differential coefficient of the real variablefunction F(x) at y=0 is ∞.

Also in the recording layer 135 shown in FIG. 10, the plan-view shape issubstantially line symmetric with respect to the perpendicular bisectorof the base of the virtual isosceles triangle.

Or, alternatively, in the nonvolatile magnetic memory device in Example2 as the nonvolatile magnetic memory device according to the seventhembodiment of the present invention, as a schematic plan view of arecording layer 135 is shown in FIG. 11, the plan-view shape of therecording layer 135 includes a first shape 135A (indicated by solid linein FIG. 11), and one projected portion 135B (indicated by solid line inFIG. 11) projected from the first shape 135A. The projected portion 135Bis located on the projected portion axis (indicated by dot-dash line inFIG. 11). Here, the projected portion axis passes through the center Oof the first shape 135A, and the projected portion axis orthogonallyintersects the first shape axis (indicated by dot-dash line in FIG. 11)passing through the center O of the first shape 135A. In addition, theeasy axis (EA) of the recording layer 135 is substantially parallel tothe first shape axis, and the hard axis (HA) of the recording layer 135is substantially parallel to the projected portion axis. Further, letthe length of the first shape 135A along the first shape axis be 2L_(L),and let the distance from a tip end portion of the projected portion135B to the center O of the first shape 135A along the projected portionaxis be L_(S), then the relationship L_(L)>L_(S) is satisfied. Besides,the portions where the visible outline of the first shape 135A and thevisible outline of the projected portion 135B intersect each other eachinclude a smooth curve (indicated by broken line in FIG. 11) curvedtoward the center O of the first shape 135A.

The first shape 135A is a flat oval, i.e., a figure composed of acombination of two semi-circles (radius: r_(L)) with two line segments.In addition, the projected portions 135B each have a figure composed ofa part of a circle (radius: r_(S)).

Incidentally, the plan-view shape of the recording layer 135 issubstantially line symmetric with respect to the projected portion axis.

Or, alternatively, in the nonvolatile magnetic memory device in Example2 as the nonvolatile magnetic memory device according to the eighthembodiment of the present invention, as a schematic plan view of arecording layer 135 is shown in FIG. 12, the plan-view shape of therecording layer 135 has a superposed shape in which a first shape 135Dand a second shape 135E are superposed on each other so that the secondshape 135E is projected from the first shape 135D at one position. Thesecond shape 135E is located on the second shape axis, which passesthrough the center O of the first shape 135D and orthogonally intersectsthe first shape axis passing through the center O of the first shape135D. Further, the easy axis (EA) of the recording layer 135 issubstantially parallel to the first shape axis, and the hard axis (HA)of the recording layer 135 is substantially parallel to the second shapeaxis. Let the length of the first shape 135D along the first shape axisbe 2L_(L), and let the distance from a tip end portion of the secondshape 135E to the center O of the first shape 135D along the secondshape axis be L_(S), then the relationship L_(L)>L_(S) is satisfied.Further, the portions where the visible outline of the first shape 135Dand the visible outline of the second shape 135E intersect each othereach have a smooth curve (indicated by broken line in FIG. 12) curvedtoward the center O of the first shape 135D.

The first shape 135D is a flat oval, i.e., a figure composed of acombination of two semi-circles (radius: r_(L)) with two line segments.The second shape 135E is a figure composed of a combination of asemi-circle (radius: r_(S)) with two line segments.

Incidentally, the plan-view shape of the recording layer 135 issubstantially line symmetric with respect to the second shape axis.

In the nonvolatile magnetic memory device including the tunnelmagnetoresistance device using the TMR effect in Example 2, let thelength of the imaginary base of the pseudo isosceles triangular shape be2L_(B), and let the virtual height be H, then a setting ofL_(B)/H=L_(L)/L_(S)=625 nm/415 nm=1.51 was adopted, as shown in FIG. 11or 12. In addition, let the average radius of curvature of the plan-viewshape of the recording layer 135 at the portions where the oblique linesSR₁ and SR₂ of the pseudo isosceles triangular shape are smoothlyconnected to the base SR₃ (or the radius of curvature of the plan-viewshape of the recording layer 135 at the intersections BC and AC betweenthe first shape axis and the plan-view shape of the recording layer 135)be r_(L), and let the radius of curvature of the plan-view shape of therecording layer 135 at the intersection AB of the two oblique lines SR₁and SR₂ of the pseudo isosceles triangular shape (or the radius ofcurvature of the plan-view shape of the recording layer 135 at theintersection AB between the projected portion axis or the second shapeaxis and the plan-view shape of the recording layer 135) be r_(S), thena setting of r_(L)/L_(S)=175 nm/415 nm=0.42 and a setting ofr_(S)/L_(L)=380 nm/625 nm=0.61 were adopted. Or, alternatively, as shownin FIG. 10, a setting of L_(i-L)/H_(i)=840 nm/420 nm=2.0 was adopted. Inaddition, let the average radius of curvature of the plan-view shape ofthe recording layer 135 at the portions where the side SR₃ constitutingthe plan-view shape of the recording layer 135 corresponding to the baseTL₃ of the virtual isosceles triangle is smoothly connected to the sidesSR₁ and SR₂ constituting the plan-view shape of the recording layer 135corresponding to the oblique lines TL₁ and TL₂ of the virtual isoscelestriangle be r_(L), and let the radius of curvature of the plan-viewshape of the recording layer 135 at the intersection AB₂ between theangular bisector at the intersection AB of the two oblique lines TL₁ andTL₂ of the virtual isosceles triangle and the plan-view shape of therecording layer 135 be r_(S), then a setting of r_(L)/H_(i)=175 nm/420nm=0.42 and a setting of r_(S)/L_(i-B)=380 nm/840 nm=0.45 were adopted.Further, in the interval 0 <X<X₁ of the oblique lines SR₁ and SR₂composed of smooth lines, let the maximum distance between the side SR₁,SR₂ and the corresponding oblique line TL₁, TL₂ of the virtual isoscelestriangle be D_(MAX), then a setting of D_(MAX)/X₁=23 nm/390 nm=0.059 wasadopted. The above-mentioned values are collectively given in Table 14below. TABLE 14 L_(B) = L_(L) = 625 nm H = L_(S) = 415 nm L_(i-B) = 840nm H_(i) = 420 nm r_(L) = 175 nm r_(S) = 380 nm D_(MAX) = 23 nm X₁ = 390nm

In the nonvolatile magnetic memory device including the tunnelmagnetoresistance device having the above data, the average H_(AVE) andthe standard deviation σ of the magnetic field H_(C) at the time ofinversion of the magnetization direction of the recording layer 135 weredetermined, in the same manner as in Example 1, and σ/H_(AVE) (SOA) wasfurther determined.

The results of Example 2 are shown in Table 15 below. In Example 1 andExample 2, the values of σ/H_(AVE) (SOA) are remarkably low. In otherwords, it is possible to largely reduce the dispersion of the switchingmagnetic field. TABLE 15 H_(AVE) (Oe) σ (Oe) σ/H_(AVE) Example 1 52.52.4 4.6% Example 2 49.8 3.8 7.6% Comparative 30.3 3.5 11.6% Example 1Comparative 37.6 4.8 12.8% Example 2

EXAMPLE 3

Example 3 pertains to a photomask according to the one embodiment of thepresent invention. The photomask in Example 3 is a photomask for use ina lithography step for forming the recording layer 35 described inExample 1 above. Specifically, the recording layer 35 is a recordinglayer constituting the magnetoresistance device in the nonvolatilemagnetic memory device, the recording layer including:

-   -   (A) a ferromagnetic material for storing information by use of        variation in resistance depending on the magnetization inversion        state thereof,    -   (B) the plan-view shape of the recording layer being a        pseudo-rhombic shape,    -   (C) the four sides SR_(m) constituting the pseudo-rhombic shape        each including a smooth curve having a central portion thereof        curved toward the center of the pseudo-rhombic shape,    -   (D) the easy axis (EA) of the recording layer being        substantially parallel to the longer axis LX of the        pseudo-rhombic shape,    -   (E) the hard axis (HA) of the recording layer being        substantially parallel to the shorter axis SX of the        pseudo-rhombic shape, and    -   (F) the sides SR_(m) being smoothly connected to each other.

As shown in FIG. 13A, a pattern provided in the photomask for obtainingthe recording layer 35 includes a first shape 51 and a second shape 52,and has a superposed shape in which the first shape 51 and the secondshape 52 having a center O coinciding with the center of the first shape51 are superposed on each other so that the second shape 52 is projectedfrom the first shape 51 at two positions. In addition, the first shapeaxis (indicated by broken line) passing through the center O of thefirst shape 51 and the second shape axis (indicated by two-dotted chainline) passing through the center O of the second shape 52 orthogonallyintersect each other.

In Example 3, the first shape 51 assumes a polygon (more specifically, arectangle) of which the length along the first shape axis substantiallyparallel to the easy axis (EA) is 2L_(p-1L) and the length along thedirection perpendicular to the first shape axis is 2L_(p-1S) [whereL_(p-1S)L_(p-1L)]. On the other hand, the second shape 52 assumes aregular polygon (more specifically, a square) of which the length alongthe second shape axis substantially parallel to the hard axis (HA) is2L_(p-2L)[where L_(p-1S)<L_(p-2L)<L_(p-1L)] and the length along thedirection passing through the center O of the second shape 52 and beingperpendicular to the second shape axis is 2L_(p-2S) [whereL_(p-2S)<L_(p-1L].)

Here, the values of 2L_(P-1L), 2L_(p-1S), 2L_(p-2L), and 2L_(p-2S) areas given in Table 16 below. By using such a pattern as this, it ispossible to obtain a recording layer 35 having a pseudo-rhombic shape asshown in FIG. 13A. Incidentally, the size data of the recording layer 35are approximate to the values shown in Table 13. TABLE 16 2L_(p-1L) =1200 nm 2L_(p-1S) = 250 nm 2L_(p-2L) = 460 nm 2L_(p-2S) = 460 nm

Incidentally, the number of the second shape(s) is not limited to one.FIG. 13B shows an example in which the number of the second shape(s) istwo.

In this example, the second shape 52 assumes a regular polygon (morespecifically, a square) of which the length along the second shape axissubstantially parallel to the hard axis (HA) is 2L_(p-2L) [whereL_(p-1S)<L_(p-2L)<L_(p-1L)] and the length along the direction passingthrough the center of the second shape 52 and being perpendicular to thesecond shape axis is 2L_(p-2S) [where L_(p-2S)<L_(P-1L)]. In addition,another second shape 53 assumes a polygon (more specifically, arectangle) of which the length along the second shape axis substantiallyparallel to the hard axis (HA) is 2L_(p-3L)[whereL_(p-2L)<Lp-3L<L_(p-1L)] and the length along the direction passingthrough the center of the other second shape 53 and being perpendicularto the second shape axis is 2L_(p-3S) [where L_(p-3S)<L_(p-2S].)

Here, the values of 2L_(P-1L), 2L_(p-1S), 2L_(p-2L), 2L_(p-2S),2L_(p-3L), and 2L_(p-3S) are as given in Table 17 below. By using such apattern as this, it is possible to obtain a recording layer 35 having apseudo-rhombic shape as shown in FIG. 13B. Incidentally, the size dataof the recording layer 35 are approximate to the values shown in Table13. TABLE 17 2L_(p-1L) = 1200 nm 2L_(p-1S) = 250 nm 2L_(p-2L) = 460 nm2L_(p-2S) = 460 nm 2L_(p-3L) = 600 nm 2L_(p-3S) = 200 nm

EXAMPLE 4

Example 4 pertains to a photomask according to the another embodiment ofthe present invention. The photomask in Example 4 is a photomask for usein a lithography step for forming the recording layer 135 described inExample 2. Specifically, the recording layer 135 is a recording layerconstituting the magnetoresistance device in the nonvolatile magneticmemory device, the recording layer including:

-   -   (A) a ferromagnetic material for storing information by use of        variation in resistance depending on the magnetization inversion        state thereof,    -   (B) the plan-view shape being a pseudo isosceles triangular        shape,    -   (C) the oblique lines SR₁ and SR₂ of the pseudo isosceles        triangular shape each including a smooth curve having a central        portion thereof curved toward the center of the pseudo isosceles        triangular shape,    -   (D) the easy axis (EA) being substantially parallel to the base        SR₃ of the pseudo isosceles triangular shape,    -   (E) the hard axis (HA) being substantially orthogonal to the        base SR₃ of the pseudo isosceles triangular shape, and    -   (F) the sides SR_(n) being smoothly connected to each other.

As shown in FIG. 14A, a pattern provided in the photomask for obtainingthe recording layer 135 includes a first shape 151 and a second shape152, and has a superposed shape in which the first shape 151 and thesecond shape 152 are superposed on each other so that the second shape152 is projected from the first shape 151 at one position. In addition,the second shape 152 is located on the second shape axis (indicated bytwo-dotted chain line). Further, the second shape axis passes throughthe center O of the first shape 151, and orthogonally intersects thefirst shape axis (indicated by broken line) passing through the center Oof the first shape 151.

In Example 4, the first shape 151 assumes a polygon (more specifically,a rectangle) of which the length along the first shape axissubstantially parallel to the easy axis (EA) is 2L_(p-1L), the lengthalong the direction passing through the center O of the first shape 151and being perpendicular to the first shape axis is 2L_(p-1S) [whereL_(p-1S)<L_(p-1L)]. On the other hand, the second shape 152 assumes apolygon (more specifically, a rectangle) of which the distance from atip end portion of the second shape 152 to the center O of the firstshape 151 along the second shape axis substantially parallel to the hardaxis (HA) is L_(p-2L)[where L_(p-1S)<L_(p-2L)<L_(P-1L)] and the lengthalong the direction passing through the center O of the first shape 151and being perpendicular to the second shape axis is 2L_(p-2S) [whereL_(p-2S)<L_(p-1L].)

Here, the values of 2L_(p-1L), 2L_(p-1S), L_(p-2L), and 2L_(p-2S) are asgiven in Table 18 below. By using such a pattern as this, it is possibleto obtain a recording layer 135 having the pseudo-rhombic shape as shownin FIG. 14A. Incidentally, the size data of the recording layer 135 areapproximate to the values shown in Table 14. TABLE 18 2L_(p-1L) = 1200nm 2L_(p-1S) = 300 nm L_(p-2L) = 310 nm 2L_(p-2S) = 460 nm

Incidentally, the number of the second shape(s) is not limited to one.FIG. 14B shows an example in which the number of the second shape(s) istwo.

In this example, a second shape 152 assumes a polygon (morespecifically, a rectangle) of which the length along the second shapeaxis substantially parallel to the hard axis (HA) is L_(p-2L)[whereL_(p-1S)<L_(p-2L)<L_(p-1L)] and the length along the direction passingthrough the center of the first shape 151 and being perpendicular to thesecond shape axis is 2L_(p-2S) [where L_(p-2S)<L_(p-1L)]. In addition,another second shape 153 assumes a polygon (more specifically, arectangle) of which the length along the second shape axis substantiallyparallel to the hard axis (HA) is L_(p-3L) [whereL_(p-2L)<L_(p-3L)<L_(P-1L)] and the length along the direction passingthrough the center of the first shape 151 and being perpendicular to thesecond shape axis is L_(p-3S) [where L_(p-3S)<L_(p-2S].)

Here, the values of 2L_(p-1L), 2L_(p-1S), L_(p-2L), 2L_(p-2S), L_(p-3L),and 2L_(p-3S) are as given in Table 19 below. By using such a pattern asthis, it is possible to obtain a recording layer 135 having thepseudo-rhombic shape as shown in FIG. 14B. Incidentally, the size dataof the recording layer 135 are approximate to the values shown in Table14. TABLE 19 2L_(p-1L) = 1200 nm 2L_(p-1S) = 300 nm L_(p-2L) = 310 nm2L_(p-2S) = 460 nm L_(p-3L) = 450 nm 2L_(p-3S) = 200 nm

While the present invention has been described above referring to thepreferred examples, the invention is not limited to these examples. Theplan-view shapes of the recording layer, the materials constituting thelayers of the magnetoresistance device, the methods of forming thelayers, the structure of the MRAM and the like described in the examplesabove are mere examples and may be modified as required. Examples of themagnetoresistance device in the nonvolatile magnetic memory deviceincludes not only the tunnel magnetoresistance device using the TMReffect described in the above examples but also a magnetoresistancedevice applying the inversion of magnetization by ion implantation, ofwhich a schematic partly sectional view is shown in FIG. 15.

This magnetoresistance device has a structure in which a combined spinfilter and reference layer 62, a tunnel insulation film 63, a recordinglayer 64, a metallic spacer layer 65, and a spin filter layer 66 arelaminated on a lower electrode 61 formed on an insulation layer 60. Thesame selection transistor TR as that shown in FIG. 6 is provided on asemiconductor substrate 10, and a source/drain region 14B on one side ofthe selection transistor TR is connected to the lower electrode 61through a contact hole 22 composed of a tungsten plug.

In addition, while a configuration in which the four sides SR_(m) eachinclude a smooth curve having a central portion thereof curved towardthe center of the pseudo-rhombic shape has been used in Example 1, analternative configuration may be adopted in which the two sides SR₁ andSR₂ each include a smooth curve having a central portion thereof curvedtoward the center of the pseudo-rhombic shape. The plan-view shape ofsuch a recording layer as this is shown in FIG. 16. In this example,when the pseudo-rhombic shape is divided into two regions by the longeraxis LX of the pseudo-rhombic shape, the two sides SR₁ and SR₂ eachincluding a smooth curve having a central portion thereof curved belongto one of the two regions. In addition, the plan-view shape of therecording layer 35 is substantially line symmetric with respect to theshorter axis SX of the pseudo-rhombic shape.

Besides, while a configuration in which the four sides SR_(m) eachinclude a smooth curve having a central portion thereof curved towardthe center of the pseudo-rhombic shape, the plan-view shape of therecording layer 35 is substantially line symmetric with respect to theshorter axis SX of the pseudo-rhombic shape, and is substantially linesymmetric with respect also to the longer axis LX of the pseudo-rhombicshape has been adopted in Example 1 above, a configuration may beadopted in which the plan-view shape of the recording layer 35 issubstantially line symmetric with respect only to the shorter axis SX ofthe pseudo-rhombic shape. The plan-view shape of such a recording layeras this is shown in FIG. 17.

The pattern constituting the photomask described in Examples 3 and 4 maybe subjected to a optical proximity correction. Examples of applicationof hammer head correction, wiring end wearout correction, inner serifcorrection, and outer serif correction to the pattern (see FIG. 18A)shown in Example 3 are exemplified in FIGS. 18B, 18C, 18D, and 18E,respectively. Incidentally, in FIGS. 18B, 18C, and 18E, the locations ofcorrection are hatched.

Examples of the data writing system include not only the direct mode inwhich a unidirectional current is passed to the write word line RWL anda positive-direction or negative-direction current is passed to the bitline depending on the data to be written, but also the toggle modedescribed in U.S. Patent Publications No. 6,545,906 B1 and 6,633,498 B1.Here, the toggle mode is a system in which a unidirectional current ispassed to the write word line RWL, a unidirectional current is passedalso to the bit line independently of the data to be written, and datais written into the magnetoresistance device only when the data recordedin the magnetoresistance device is different from the data to bewritten.

The data reading can be carried out by use of the data read line,without using the bit line. In this case, the bit line is formed on theupper side of the recording layer (the second ferromagnetic materiallayer) in the state of being electrically insulated from the recordinglayer (the second ferromagnetic material layer) by the upper interlayerinsulation layer. Then, the data read line electrically connected to therecording layer (the second ferromagnetic material layer) may beprovided separately.

1. A nonvolatile magnetic memory device comprising a magentoresistancedevice having a recording layer formed of a ferromagnetic material forstoring information by use of variation in resistance depending on themagnetization inversion state; wherein the plan-view shape of saidrecording layer is a pseudo-rhombic shape; at least two of the foursides constituting said pseudo-rhombic shape each include a smooth curvehaving a central portion curved toward the center of said pseudo-rhombicshape; the easy axis of magnetization of said recording layer issubstantially parallel to the longer axis of said pseudo-rhombic shape;the hard axis of magnetization of said recording layer is substantiallyparallel to the shorter axis of said pseudo-rhombic shape; and the sidesconstituting the plan-view shape of said recording layer are smoothlyconnected to each other.
 2. The nonvolatile magnetic memory device asset forth in claim 1, wherein there are at least two points ofinflection in each of said sides each including said smooth curve havingthe central portion curved.
 3. The nonvolatile magnetic memory device asset forth in claim 1, wherein when said pseudo-rhombic shape is dividedinto two regions by the longer axis of said pseudo-rhombic shape, saidtwo sides each including said smooth curve having the central portioncurved belong to one of said regions.
 4. The nonvolatile magnetic memorydevice as set forth in claim 1, wherein said four sides each include asmooth curve having a central portion curved toward the center of saidpseudo-rhombic shape.
 5. The nonvolatile magnetic memory device as setforth in claim 1, wherein said plan-view shape of said recording layeris substantially line symmetric with respect to the shorter axis of saidpseudo-rhombic shape.
 6. The nonvolatile magnetic memory device as setforth in claim 5, wherein said plan-view shape of said recording layeris substantially line symmetric with respect to the longer axis of saidpseudo-rhombic shape.
 7. A nonvolatile magnetic memory device comprisinga magnetoresistance device having a recording layer formed of aferromagnetic material for storing information by use of variation inresistance depending on the magnetization inversion state; wherein theplan-view shape of said recording layer includes four sides; at leasttwo of said four sides each include a smooth curve; said plan-view shapeof said recording layer is inscribed in a virtual rhombus having alonger axis, and a shorter axis orthogonally intersecting said longeraxis at the bisecting point of said longer axis, said longer axis beingsubstantially parallel to the easy axis of magnetization of saidrecording layer, and said shorter axis being substantially parallel tothe hard axis of magnetization of said recording layer; each of saidsides each including said smooth curve contacts the corresponding sideof said virtual rhombus at at least two points; and said sidesconstituting said plan-view shape of said recording layer are smoothlyconnected to each other.
 8. The nonvolatile magnetic memory device asset forth in claim 7, wherein when, in each of said sides constitutingsaid plan-view shape of said recording layer and each including thesmooth curve, (a) the point located closest to said shorter axis of saidvirtual rhombus, of said at least two points of contact with the side ofsaid virtual rhombus, is made to be the origin (0, 0) of a Gaussiancoordinate system, (b) the point located closest to said longer axis ofsaid virtual rhombus, of said at least two points of contact with theside of said virtual rhombus, is made to be (X₁, 0) [where X₁>0], (c)the intersection with the shorter axis of said virtual rhombus is madeto be (X_(S), Y_(S)) [where X_(S)<0, Y_(S)<0], (d) the intersection withthe longer axis of said virtual rhombus is made to be (X_(L), Y_(L))[where X_(L)>0, Y_(L)<0]; and said side is represented by a realvariable function F(X), and the intersection of said longer axis andsaid shorter axis of said virtual rhombus is located in the thirdquadrant or the fourth quadrant; then said real variable function F(X)has a continuous differential coefficient at each point in an intervalX_(S)<X<X_(L), and said real variable function F(X) has at least twopoints of inflection in an interval 0<X<X₁.
 9. The nonvolatile magneticmemory device as set forth in claim 7, wherein said plan-view shape ofsaid recording layer is substantially line symmetric with respect tosaid shorter axis of said virtual rhombus.
 10. The nonvolatile magneticmemory device as set forth in claim 7; wherein the four sides in saidplan-view shape of said recording layer each include a smooth curve; andsaid plan-view shape of said recording layer is substantially linesymmetric with respect to the shorter axis of said virtual rhombus, andis substantially line symmetric with respect to said longer axis of saidvirtual rhombus.
 11. A nonvolatile magnetic memory device comprising amagnetoresistance device having a recording layer formed of aferromagnetic material for storing information by use of variation inresistance depending on the magnetization inversion state; wherein theplan-view shape of said recording layer has a first shape, and twoprojected portions oppositely projected from said first shape; said twoprojected portions are positioned on the projected portion axis; theaxis of each said projected portions passes through the center of saidfirst shape and orthogonally intersects the first shape axis passingthrough the center of said first shape; said first shape includes oneshape selected from the group including an ellipse, a flat oval, and aflat circle; said projected portions each include one shape selectedfrom the group including a part of a circle, a part of an ellipse, apart of a flat oval, and a part of a flat circle; the easy axis ofmagnetization of said recording layer is substantially parallel to saidfirst shape axis; the hard axis of magnetization of said recording layeris substantially parallel to the projected portion axis; therelationship L_(L)>L_(S) is satisfied, where 2L_(L) is the length ofsaid first shape along said first shape axis, and 2L_(S) is the distancebetween the tip ends of said two projected portions along said projectedportion axis; and the portion at which the visible outline of said firstshape and the visible outline of each side projected portion intersectincludes a smooth curve.
 12. The nonvolatile magnetic memory device asset forth in claim 11, wherein the plan-view shape of said recordinglayer is substantially line symmetric with respect to said projectedportion axis, and is substantially line symmetric with respect to saidfirst shape axis.
 13. A nonvolatile magnetic memory device comprising amagnetoresistance device having a recording layer formed of aferromagnetic material for storing information by use of variation inresistance depending on the magnetization inversion state; wherein theplan-view shape of said recording layer is a superposed shape in which afirst shape and a second shape having a center coinciding with thecenter of said first shape are superposed on each other so that saidsecond shape is projected from said first shape at two positions; thefirst shape axis passing through the center of said first shape and thesecond shape axis passing through the center of said second shapeorthogonally intersect each other; said first shape includes one shapeselected from the group including an ellipse, a flat oval, and a flatcircle; said second shape includes one shape selected from the groupincluding a circle, an ellipse, a flat oval, and a flat circle; the easyaxis of magnetization of said recording layer is substantially parallelto said first shape axis; the hard axis of magnetization of saidrecording layer is substantially parallel to said second shape axis; therelationship L_(L)>L_(S) is satisfied, where 2L_(L) is the length ofsaid first shape along said first shape axis, and 2L_(S) is the lengthof the second shape along said second shape axis; and the portion atwhich the visible outline of said first shape and the visible outline ofsaid second shape intersect each other includes a smooth curve.
 14. Thenonvolatile magnetic memory device as set forth in claim 13, whereinsaid plan-view shape of said recording layer is substantially linesymmetric with respect to said second shape axis, and is substantiallyline symmetric with respect to said first shape axis.
 15. A nonvolatilemagnetic memory device comprising a magnetoresistance device having arecording layer formed of a ferromagnetic material for storinginformation by use of variation in resistance depending on themagnetization inversion state; wherein the plan-view shape of saidrecording layer includes a pseudo isosceles triangular shape; theoblique lines of said pseudo isosceles triangular shape each include asmooth curve having a central portion curved toward the center of saidpseudo isosceles triangular shape; the length of the imaginary base ofsaid pseudo isosceles triangular shape is greater than the virtualheight of said pseudo isosceles triangular shape; the easy axis ofmagnetization of said recording layer is substantially parallel to saidbase of said pseudo isosceles triangular shape; the hard axis ofmagnetization of said recording layer is substantially orthogonal tosaid base of said pseudo isosceles triangular shape; and the sidesconstituting said plan-view shape of said recording layer are smoothlyconnected to each other.
 16. The nonvolatile magnetic memory device asset forth in claim 15, wherein at least two points of inflection arepresent in each of the oblique lines of said pseudo isosceles triangularshape.
 17. The nonvolatile magnetic memory device as set forth in claim15, wherein said plan-view shape of said recording layer issubstantially line symmetric with respect to the perpendicular bisectorof the imaginary base of said pseudo isosceles triangular shape.
 18. Anonvolatile magnetic memory device comprising a magnetoresistance devicehaving a recording layer formed of a ferromagnetic material for storinginformation by use of variation in resistance depending on themagnetization inversion state; wherein the plan-view shape of saidrecording layer includes three sides; at least two of said three sideseach include a smooth curve; said plan-view shape of said recordinglayer is inscribed in a virtual isosceles triangle in which the lengthof the imaginary base is 2L_(i-B), the virtual height is H_(i) [whereH_(i)<L_(i-B)], said base is substantially parallel to the easy axis ofmagnetization of said recording layer, and the perpendicular to saidbase is substantially parallel to the hard axis of magnetization of saidrecording layer; each of said sides each including the smooth curvecontacts an oblique line of said virtual isosceles triangle at at leasttwo points; and said sides constituting said plan-view shape of saidrecording layer are smoothly connected to each other.
 19. Thenonvolatile magnetic memory device as set forth in claim 18; whereinwhen, in each of said sides each including the smooth curve andconstituting said plan-view shape of said recording layer, (a) the pointclosest to the intersection between said two oblique lines of saidvirtual isosceles triangle, of at least two points of contact with saidoblique line, is made to be the origin (0, 0) of a Gaussian coordinatesystem, (b) the point closest to the intersection between said obliqueline and said base of said virtual isosceles triangle, of at least twopoints of contact with said oblique line, is made to be (X₁, 0) [whereX₁>0], (c) the intersection with the perpendicular bisector of saidimaginary base of said virtual isosceles triangle is made to be (X_(S),Y_(S)) [where X_(S)<0, Y_(S)<0], (d) the intersection with saidimaginary base of said virtual isosceles triangle is made to be (X_(L),Y_(L)) [where X_(L)>0, Y_(L)<0]; and said side is represented by a realvariable function F(X), and the intersection between the perpendicularbisector of said base of said virtual isosceles triangle and said baseof said virtual isosceles triangle is located in the third quadrant orthe fourth quadrant; said real variable function F(X) has a continuousdifferential coefficient at each point in an interval X_(S)<X<X_(L); andsaid real variable function F(X) has at least two points of inflectionin an interval 0<X<X₁.
 20. The nonvolatile magnetic memory device as setforth in claim 18, wherein said plan-view shape of said recording layeris substantially line symmetric with respect to said perpendicularbisector of said base of said virtual isosceles triangle.
 21. Anonvolatile magnetic memory device comprising a magnetoresistance devicehaving a recording layer formed of a ferromagnetic material for storinginformation by use of variation in resistance depending on themagnetization inversion state; wherein the plan-view shape of saidrecording layer includes a first shape, and a projected portionprojected from said first shape; said projected portion is located onthe projected portion axis; said projected portion axis passes throughthe center of said first shape, and orthogonally intersects the firstshape axis passing through the center of said first shape; said firstshape has one shape selected from the group including an ellipse, a flatoval, and a flat circle; said projected portion has one shape selectedfrom the group including a part of a circle, a part of an ellipse, apart of a flat oval, and a part of a flat circle; the easy axis ofmagnetization of said recording layer is substantially parallel to saidfirst shape axis; the hard axis of magnetization of said recording layeris substantially parallel to said projected portion axis; therelationship L_(L)>L_(S) is satisfied, where 2L_(L) is the length ofsaid first shape along said first shape axis, and L_(S) is the distancefrom a tip end portion of said projected portion to the center of saidfirst shape along said projected portion axis; and the portion at whichthe visible outline of said first shape and the visible outline of saidprojected portion intersect includes a smooth curve.
 22. The nonvolatilemagnetic memory device as set forth in claim 21, wherein said plan-viewshape of said recording layer is substantially line symmetric withrespect to said projected portion axis.
 23. A nonvolatile magneticmemory device comprising a magnetoresistance device having a recordinglayer formed of a ferromagnetic material for storing information by useof variation in resistance depending on the magnetization inversionstate; wherein the plan-view shape of said recording layer is asuperposed shape in which a first shape and a second shape aresuperposed on each other so that said second shape is projected fromsaid first shape at one position; said second shape is located on thesecond shape axis; said second shape axis passes through the center ofsaid first shape, and orthogonally intersects the first shape axispassing through the center of said first shape; said first shape has oneshape selected from the group including an ellipse, a flat oval, and aflat circle; said second shape has one shape selected from the groupincluding a circle, an ellipse, a flat oval, and a flat circle; the easyaxis of magnetization of said recording layer is substantially parallelto said first shape axis; the hard axis of magnetization of saidrecording layer is substantially parallel to said second shape axis; therelationship L_(L)>L_(S) is satisfied, where 2L_(L) is the length ofsaid first shape along said first shape axis, and L_(S) is the distancefrom a tip end portion of said second shape to the center of said firstshape along said second shape axis; and the portion at which the visibleoutline of said first shape and the visible outline of said second shapeintersect includes a smooth curve.
 24. The nonvolatile magnetic memorydevice as set forth in claim 23, wherein said plan-view shape of saidrecording layer is substantially line symmetric with respect to saidsecond shape axis.
 25. The nonvolatile magnetic memory device as setforth in any of claims 1 to 24; wherein said magnetoresistance devicehas a tunnel magnetoresistance device having a laminate structure of afirst ferromagnetic material layer, a tunnel insulation film, and asecond ferromagnetic material layer which are provided in this orderfrom the lower side; and said recording layer includes said secondferromagnetic material layer.
 26. The nonvolatile magnetic memory deviceas set forth in claim 25; wherein a first wiring extending in a firstdirection, having a conductor layer, and being electrically insulatedfrom said first ferromagnetic material layer is provided on the lowerside of said first ferromagnetic material layer, through a lowerinterlayer insulation layer; and a second wiring extending in a seconddirection different from said first direction, having a conductor layer,and being electrically connected to said second ferromagnetic materiallayer or electrically isolated from said second ferromagnetic materiallayer is provided on the upper side of said second ferromagneticmaterial layer, through an upper interlayer insulation layer.
 27. Thenonvolatile magnetic memory device as set forth in claim 26, furthercomprising a selection transistor including a field effect transistorprovided on the lower side of said first wiring, through an interlayerinsulation layer, wherein said first ferromagnetic material layer iselectrically connected to one of source/drain regions of said selectiontransistor.
 28. A photomask for use in a lithography step for forming arecording layer constituting a magnetoresistance device in a nonvolatilemagnetic memory device, said recording layer comprising: (A) aferromagnetic material for storing information by use of variation inresistance depending on the magnetization inversion state; (B) theplan-view shape of said recording layer being a pseudo-rhombic shape;(C) the sides constituting said pseudo-rhombic shape each including asmooth curve having a central portion curved toward the center of saidpseudo-rhombic shape; (D) the easy axis of magnetization of saidrecording layer being substantially parallel to the longer axis of saidpseudo-rhombic shape; (E) the hard axis of magnetization of saidrecording layer being substantially parallel to the shorter axis of saidpseudo-rhombic shape; and (F) said sides being smoothly connected toeach other; wherein said photomask is provided with a pattern having afirst shape and a second shape, in which said first shape and saidsecond shape having a center coinciding with the center of said firstshape are superposed on each other so that said second shape isprojected from said first shape at two positions; the first shape axispassing through the center of said first shape and the second shape axispassing through the center of said second shape orthogonally intersecteach other; said first shape has one shape selected from the groupincluding a regular polygon, an ellipse, a flat oval, and a flat circleof which the length along said first shape axis substantially parallelto said easy axis is 2L_(p-1L), and the length along the directionperpendicular to said first shape axis is 2L_(p-1S) [whereL_(p-1S)<L_(P-1L)]; and said second shape has one shape selected fromthe group including a regular polygon, a circle, an ellipse, a flatoval, and a flat circle of which the length along said second shape axissubstantially parallel to said hard axis is 2L_(p-2L) [whereL_(p-1S)<L_(p-2L)<L_(p-1L)], and the length along the directionperpendicular to said second shape axis is 2L_(p-2S) [whereL_(p-2S)<L_(p-1L].)
 29. A photomask for use in a lithography step forforming a recording layer constituting a magnetoresistance device in anonvolatile magnetic memory device, said recording layer comprising: (A)a ferromagnetic material for storing information by use of variation inresistance depending on the magnetization inversion state; (B) theplan-view shape of said recording layer being a pseudo isoscelestriangular shape; (C) the oblique lines of said pseudo isoscelestriangular shape each including a smooth curve having a central portioncurved toward the center of said pseudo isosceles triangular shape; (D)the easy axis of magnetization of said recording layer beingsubstantially parallel to the base of said pseudo isosceles triangularshape; (E) the hard axis of magnetization of said recording layer beingsubstantially orthogonal to the base of said pseudo isosceles triangularshape; and (F) the sides of said plan-view shape being smoothlyconnected to each other; wherein said photomask is provided with apattern has a first shape and a second shape, in which said first shapeand said second shape are superposed on each other so that said secondshape is projected from said first shape at one position; said secondshape is located on the second shape axis; said second shape axis passesthrough the center of said first shape, and orthogonally intersects thefirst shape axis passing through the center of said first shape; saidfirst shape has one shape selected from the group including a regularpolygon, an ellipse, a flat oval, and a flat circle of which the lengthalong said first shape axis substantially parallel to said easy axis is2L_(p-1L), and the length along the direction passing through the centerof said first shape and being perpendicular to said first shape axis is2L_(p-1S) [where L_(p-1S)<L_(p-1L)]; and said second shape has one shapeselected from the group including a regular polygon, a circle, anellipse, a flat oval, and a flat circle of which the distance from a tipend portion of said second shape to the center of said first shape alongsaid second shape axis substantially parallel to said hard axis isL_(p-2L)[where L_(p-1S)<L_(p-2L)<L_(p-1L)], and the length along thedirection passing through the center of said first shape and beingperpendicular to said second shape axis is 2L_(p-2S)[whereL_(p-2S)<L_(p-1L)].